Modify h323 to build against PTLib as well as the older PWLib

Several changes in PTLib have occurred requiring build time detection. Changes
accounted for include the library name change, config option change, install
location change, and a boolean type change which is handled by ast_ptlib.h.
Also, the sed check has been modified to properly work with autoconf >= 2.62.

(closes issue #14224)
Reported by: bergolth
Patches:
      asterisk-autoconf-sed.patch uploaded by bergolth (license 661)
      asterisk-pwlib-v3.patch uploaded by bergolth (license 661)
Tested by: jpeeler


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@177162 65c4cc65-6c06-0410-ace0-fbb531ad65f3