Issues in pjproject 2.9 caused us to revert some of their changes
as a work around.  This introduced another issue where pjproject
wouldn't build with older gcc versions such as that found on
CentOS 6.  This commit replaces the reverts with the official
fixes for the original issues and allows pjproject to be built
on CentOS 6 again.

ASTERISK-28574
Reported-by: Niklas Larsson

Change-Id: I06f8507bea553d1a01b0b8874197d35b9d47ec4c