general: Fix broken links.

This fixes a number of broken links throughout the
tree, mostly caused by wiki.asterisk.org being replaced
with docs.asterisk.org, which should eliminate the
need for sporadic fixes as in f28047db36.

Resolves: #430

apps/app_audiosocket.c

@@ -61,7 +61,7 @@
 		</syntax>
 		<description>
 			<para>Connects to the given TCP service, then transmits channel audio over that socket.  In turn, audio is received from the socket and sent to the channel.  Only audio frames will be transmitted.</para>
-			<para>Protocol is specified at https://wiki.asterisk.org/wiki/display/AST/AudioSocket</para>
+			<para>Protocol is specified at https://docs.asterisk.org/Configuration/Channel-Drivers/AudioSocket/</para>
 			<para>This application does not automatically answer and should generally be preceeded by an application such as Answer() or Progress().</para>
 		</description>
 	</application>

apps/app_skel.c

@@ -16,7 +16,7 @@
  * at the top of the source tree.
  *
  * Please follow coding guidelines
- * https://wiki.asterisk.org/wiki/display/AST/Coding+Guidelines
+ * https://docs.asterisk.org/Development/Policies-and-Procedures/Coding-Guidelines/
  */
 
 /*! \file

apps/app_voicemail.c

@@ -27,7 +27,7 @@
  *
  * \par See also
  * \arg \ref voicemail.conf "Config_voicemail"
- * \note For information about voicemail IMAP storage, https://wiki.asterisk.org/wiki/display/AST/IMAP+Voicemail+Storage
+ * \note For information about voicemail IMAP storage, https://docs.asterisk.org/Configuration/Applications/Voicemail/IMAP-Voicemail-Storage/
  * \ingroup applications
  * \todo This module requires res_adsi to load. This needs to be optional
  * during compilation.

apps/confbridge/include/conf_state.h

@@ -22,7 +22,7 @@
  *
  * \author\verbatim Terry Wilson <twilson@digium.com> \endverbatim
  *
- * See https://wiki.asterisk.org/wiki/display/AST/Confbridge+state+changes for
+ * See https://docs.asterisk.org/Development/Reference-Information/Other-Reference-Information/Confbridge-state-changes/ for
  * a more complete description of how conference states work.
  */