build-system: Allow building with static pjproject

Background here:
http://lists.digium.com/pipermail/asterisk-dev/2016-January/075266.html

From CHANGES:
 * To help insure that Asterisk is compiled and run with the same known
   version of pjproject, a new option (--with-pjproject-bundled) has been
   added to ./configure.  When specified, the version of pjproject specified
   in third-party/versions.mak will be downloaded and configured.  When you
   make Asterisk, the build process will also automatically build pjproject
   and Asterisk will be statically linked to it.  Once a particular version
   of pjproject is configured and built, it won't be configured or built
   again unless you run a 'make distclean'.

   To facilitate testing, when 'make install' is run, the pjsua and pjsystest
   utilities and the pjproject python bindings will be installed in
   ASTDATADIR/third-party/pjproject.

   The default behavior remains building with the shared pjproject
   installation, if any.

Building:

   All you have to do is include the --with-pjproject-bundled option on
   the ./configure command line (and remove any existing --with-pjproject
   option if specified).  Everything else is automatic.

Behind the scenes:

   The top-level Makefile was modified to include 'third-party' in the
   list of MOD_SUBDIRS.

   The third-party directory was created to contain any third party
   packages that may be needed in the future.  Its Makefile automatically
   iterates over any subdirectories passing on targets.

   The third-party/pjproject directory was created to house the pjproject
   source distribution.  Its Makefile contains targets to download, patch
   configure, generate dependencies, compile libs, apps and python bindings,
   sanitized build.mak and generate a symbols list.

   When bootstrap.sh is run, it automatically includes the configure.m4
   file in third-party/pjproject.  This file has a macro to download and
   conifgure pjproject and get and set PJPROJECT_INCLUDE, PJPROJECT_DIR
   and PJPROJECT_BUNDLED.  It also tests for the capabilities like
   PJ_TRANSACTION_GRP_LOCK by parsing preprocessor output as opposed to
   trying to compile.  Of course, bootstrap.sh is only run once and the
   configure file is incldued in the patch.

   When configure is run with the new options, the macro in configure.m4
   triggers the download, patch, conifgure and tests.  No compilation is
   performed at this time.  The downloaded tarball is cached in /tmp so
   it doesn't get downloaded again on a distclean.

   When make is run in the top-level Asterisk source directory, it will
   automatically descend all the subdirectories in third_party just as it
   does for addons, apps, etc.  The top-level Makefile makes sure that
   the 'third-party' is built before 'main' so that dependencies from the
   other directories are built first.

   When main does build, a new shared library (libasteriskpj) is created that
   links statically to the pjproject .a files and exports all their symbols.
   The asterisk binary links to that, just as it does with libasteriskssl.

   When Asterisk is installed, the pjsua and pjsystest apps, and the pjproject
   python bindings are installed in ASTDATADIR/third-party/pjproject.  This
   will facilitate testing, including running the testsuite which will be
   updated to check that directory for the pjsua module ahead of the system
   python library.

Modules should continue to depend on pjproject if they use pjproject APIs
directly.  They should not care about the implementation.  No changes to any
res_pjsip modules were made.

Change-Id: Ia7a60c28c2e9ba9537c5570f933c1ebcb20a3103

include/asterisk/_private.h

@@ -52,6 +52,7 @@ void ast_stun_init(void);               /*!< Provided by stun.c */
 int ast_cel_engine_init(void);		/*!< Provided by cel.c */
 int ast_cel_engine_reload(void);	/*!< Provided by cel.c */
 int ast_ssl_init(void);                 /*!< Provided by ssl.c */
+int ast_pj_init(void);                 /*!< Provided by libasteriskpj.c */
 int ast_test_init(void);            /*!< Provided by test.c */
 int ast_msg_init(void);             /*!< Provided by message.c */
 void ast_msg_shutdown(void);        /*!< Provided by message.c */

include/asterisk/autoconfig.h.in

@@ -155,13 +155,13 @@
 /* Define to 1 if you have the `cosl' function. */
 #undef HAVE_COSL
 
-/* Define to 1 if you have the `crypt' function. */
+/* Define to 1 if you have the 'crypt' function. */
 #undef HAVE_CRYPT
 
 /* Define to 1 if you have the OpenSSL Cryptography library. */
 #undef HAVE_CRYPTO
 
-/* Define to 1 if you have the `crypt_r' function. */
+/* Define to 1 if you have the 'crypt_r' function. */
 #undef HAVE_CRYPT_R
 
 /* Define to 1 if you have a functional curl library. */
@@ -581,22 +581,25 @@
 /* Define if your system has the PJPROJECT libraries. */
 #undef HAVE_PJPROJECT
 
-/* Define to 1 if PJPROJECT has the PJSIP Dialog Create UAS with Incremented
-   Lock feature. */
+/* Define if your system has PJPROJECT_BUNDLED */
+#undef HAVE_PJPROJECT_BUNDLED
+
+/* Define if your system has pjsip_dlg_create_uas_and_inc_lock declared. */
 #undef HAVE_PJSIP_DLG_CREATE_UAS_AND_INC_LOCK
 
-/* Define to 1 if PJPROJECT has the pjsip_get_dest_info support feature. */
+/* Define if your system has pjsip_endpt_set_ext_resolver declared. */
+#undef HAVE_PJSIP_EXTERNAL_RESOLVER
+
+/* Define if your system has pjsip_get_dest_info declared. */
 #undef HAVE_PJSIP_GET_DEST_INFO
 
 /* Define if your system has the PJSIP_REPLACE_MEDIA_STREAM headers. */
 #undef HAVE_PJSIP_REPLACE_MEDIA_STREAM
 
-/* Define to 1 if PJPROJECT has the pj_ssl_cert_load_from_files2 support
-   feature. */
+/* Define if your system has pj_ssl_cert_load_from_files2 declared. */
 #undef HAVE_PJ_SSL_CERT_LOAD_FROM_FILES2
 
-/* Define to 1 if PJPROJECT has the PJSIP Transaction Group Lock Support
-   feature. */
+/* Define if your system has pjsip_tsx_create_uac2 declared. */
 #undef HAVE_PJ_TRANSACTION_GRP_LOCK
 
 /* Define to 1 if your system defines IP_PKTINFO. */