Add dg-require-effective-target exceptions

There are a number of tests that fail because they assume that exceptions are
available, but GCN does not support them, yet.

This patch adds "dg-require-effective-target exceptions" in all the affected
tests.  There's probably an automatic way to test for exceptions, but the
current implementation simply says that AMD GCN does not support them.  This
should ensure that no other targets are affected by the change.

2019-01-17  Andrew Stubbs  <ams@codesourcery.com>
	    Kwok Cheung Yeung  <kcy@codesourcery.com>
	    Julian Brown  <julian@codesourcery.com>
	    Tom de Vries  <tom@codesourcery.com>

	gcc/
	* doc/sourcebuild.texi: Document dg-required-effective-target
	exceptions.

	gcc/testsuite/
	* c-c++-common/ubsan/pr71512-1.c: Require exceptions.
	* c-c++-common/ubsan/pr71512-2.c: Require exceptions.
	* gcc.c-torture/compile/pr34648.c: Require exceptions.
	* gcc.c-torture/compile/pr41469.c: Require exceptions.
	* gcc.dg/20111216-1.c: Require exceptions.
	* gcc.dg/cleanup-10.c: Require exceptions.
	* gcc.dg/cleanup-11.c: Require exceptions.
	* gcc.dg/cleanup-12.c: Require exceptions.
	* gcc.dg/cleanup-13.c: Require exceptions.
	* gcc.dg/cleanup-5.c: Require exceptions.
	* gcc.dg/cleanup-8.c: Require exceptions.
	* gcc.dg/cleanup-9.c: Require exceptions.
	* gcc.dg/gomp/pr29955.c: Require exceptions.
	* gcc.dg/lto/pr52097_0.c: Require exceptions.
	* gcc.dg/nested-func-5.c: Require exceptions.
	* gcc.dg/pch/except-1.c: Require exceptions.
	* gcc.dg/pch/valid-2.c: Require exceptions.
	* gcc.dg/pr41470.c: Require exceptions.
	* gcc.dg/pr42427.c: Require exceptions.
	* gcc.dg/pr44545.c: Require exceptions.
	* gcc.dg/pr47086.c: Require exceptions.
	* gcc.dg/pr51481.c: Require exceptions.
	* gcc.dg/pr51644.c: Require exceptions.
	* gcc.dg/pr52046.c: Require exceptions.
	* gcc.dg/pr54669.c: Require exceptions.
	* gcc.dg/pr56424.c: Require exceptions.
	* gcc.dg/pr64465.c: Require exceptions.
	* gcc.dg/pr65802.c: Require exceptions.
	* gcc.dg/pr67563.c: Require exceptions.
	* gcc.dg/tree-ssa/pr41469-1.c: Require exceptions.
	* gcc.dg/tree-ssa/ssa-dse-28.c: Require exceptions.
	* gcc.dg/vect/pr46663.c: Require exceptions.
	* lib/target-supports.exp (check_effective_target_exceptions): New.


Co-Authored-By: Julian Brown <julian@codesourcery.com>
Co-Authored-By: Kwok Cheung Yeung <kcy@codesourcery.com>
Co-Authored-By: Tom de Vries <tom@codesourcery.com>

From-SVN: r268025