Revert 2015-11-09 sanitizer/obstack configury

Revert 2015-11-09 sanitizer/obstack configury

The 2015-11-23 sanitizer merge from upstream lost the changes from
f6528435 to sanitizer_common/sanitizer_common_interceptors.inc, which
made use of _OBSTACK_SIZE_T.  So the configury changes to define
_OBSTACK_SIZE_T don't do anything.  This wasn't such a bad thing
anyway..  The configure test wrongly adds -I${srcdir}/../include,
effectively resulting in a test of libiberty/obstack rather than libc
obstack support, and it's the latter that asan and tsan need to work
with.

So, remove the useless configure test.  Upstream santizer project has
been made aware of the problem if glibc obstack support is ever
updated.  Bootsrapped etc. x86_64-linux and committed as obvious.

	Revert 2015-11-09  Alan Modra  <amodra@gmail.com>
	* configure.ac: Don't substitute OBSTACK_DEFS.
	* asan/Makefile.am: Remove OBSTACK_DEFS from DEFS.
	* tsan/Makefile.am: Likewise.
	* configure: Regenerate.
	* Makefile.in: Regenerate.
	* asan/Makefile.in: Regenerate.
	* interception/Makefile.in: Regenerate.
	* libbacktrace/Makefile.in: Regenerate.
	* lsan/Makefile.in: Regenerate.
	* sanitizer_common/Makefile.in: Regenerate.
	* tsan/Makefile.in: Regenerate.
	* ubsan/Makefile.in: Regenerate.

From-SVN: r238701