The STLport was only built for the benefit of old extensions on platforms that
once used it themselves (Linux x86, Solaris x86 and SPARC, Windows).  We
deliberately break such old extensions for LO 4.0 by no longer shipping that
backwards-compatiblity cludge.

Keeps STLport listed in readlicense_oo/ because of
o3tl/inc/o3tl/compat_functionality.hxx.

Also removes GXX_INCLUDE_PATH, as that was only used by STLport (if at all?).

(cherry picked from commit 77d3777c, minus the
code that addressed Windows C4005 warnings -- which after all were due to
unrelated changes for PCH rather than this commit)
Conflicts:
	postprocess/prj/build.lst

Change-Id: Ie138a219fbbc86fb5aaa7ea0b88cf349935d9829