Allow H.323 Plus library to be used in addition to the OpenH323 library

Chan_h323 can now be compiled against both the previously supported versions of
OpenH323 as well as the current H.323 Plus (version 1.20.2). The configure
script has been modified to look in the default install location of h323 to
hopefully help avoid using the environment variables OPENH323DIR and PWLIBDIR.
Also, the CLI command "h323 show version" has been added which indicates which
version of h323 is in use.

(closes issue #11261)
Reported by: vhatz
Patches:
      asterisk-1.6.0.6-h323plus.patch uploaded by jthurman (license 614)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@182722 65c4cc65-6c06-0410-ace0-fbb531ad65f3