opus

Completely remove the built-in autotools -fstatck-protector detection.

 On some systems (HPPA+HPUX+GCC) -fstatck-protector was causing failures not
at build or link time but at actual runtime. This is much less reasonable to
detect from autotools. It looks this this really can only safely be a white-
list, and the systems which would be whitelisted often already pick up the
setting from the OS build environment in any case.  It isn't important for
OPUS, we were just using it as belt-and-suspenders security and because it
makes some failure types easier to troubleshoot.