res_pjproject: Add module providing pjproject logging and utils

res_pjsip_log_forwarder has been renamed to res_pjproject
and enhanced as follows:

As a follow-on to the recent 'Add CLI "pjsip show buildopts"' patch,
a new ast_pjproject_get_buildopt function has been added.  It
allows the caller to get the value of one of the buildopts.

The initial use case is retrieving the runtime value of
PJ_MAX_HOSTNAME to insure we don't send a hostname greater
than pjproject can handle.  Since it can differ between
the version of pjproject that Asterisk was compiled against
and the version of pjproject that Asterisk is running against,
we can't use the PJ_MAX_HOSTNAME macro directly in Asterisk
source code.

Change-Id: Iab6e82fec3d7cf00c1cf6185c42be3e7569dee1e