For all OSes:
* Disabled third-party codecs in pjproject and added
  '--disable-speex-codec --disable-speex-aec --disable-gsm-codec' to the
  configure options since we don't use the pjsip codec capability.

FreeBSD:
* Added FreeBSD support to install_prereq.
* Changed pjproject/configure.m4 to use $GNU_MAKE instead of hardcoding "make".
* Added __progname and environ to asterisk.exports.in.
* Reverted the use of ldconfig to create shared library symlinks to ln.
* Only enable epoll in pjproject if `uname -s` is Linux.
* Added a patch to pjproject to take the name of the 'make' command from
  an environment variable if supplied.  This is needed for the python bindings.
  (merged by Teluu into pjproject trunk 5/3/2016)
FreeBSD support isn't complete.  Still some general issues regarding
make/gmake having nothing to do with pjproject.  With some handholding it DOES
build successfully.

CentOS:
Added 'patch' and 'bzip2' to install_prereq PACKAGES_RH.
CentOS 6/7 32/64 build and run the pjsip testsuite successfully.

Ubuntu:
No changes required.
Ubuntu 15/16 32/64 build and run the pjsip testsuite successfully.

Debian:
No changes required.
Debian 6/7/8 32/64 build and run the pjsip testsuite successfully.

There will utimately be a follow-up patch to create an install_prereq for
the testsuite as I've discovered a few missing requirements.

ASTERISK-25968 #close

Change-Id: I5756a07facfc63798115a5e73a8709382fe9259c