Fix Record-Route parsing for large headers.

Record-Route parsing copied the header into a char[256] array, which can
be a problem if the header is longer than that. This patch parses the
header in place, without the copy, avoiding the issue.

In addition to the original patch, I added a unit test for the new
get_in_brackets_const function.

(closes issue ASTERISK-20837)
Reported by: Corey Farrell
Patches:
	chan_sip-build_route-optimized-rev1.patch uploaded by Corey Farrell (license 5909)
	(with minor changes by dlee)
........

Merged revisions 379392 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@379393 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/sip/include/reqresp_parser.h

@@ -90,6 +90,17 @@ int get_name_and_number(const char *hdr, char **name, char **number);
  */
 char *get_in_brackets(char *tmp);
 
+/*! \brief Get text in brackets on a const without copy
+ *
+ * \param src String to search
+ * \param[out] start Set to first character inside left bracket.
+ * \param[out] length Set to lenght of string inside brackets
+ * \retval 0 success
+ * \retval -1 failure
+ * \retval 1 no brackets so got all
+ */
+int get_in_brackets_const(const char *src,const char **start,int *length);
+
 /*! \brief Get text in brackets and any trailing residue
  *
  * \retval 0 success