Skip test 'watch -location nullptr->p->x' if null pointer can be dereferenced

gdb.base/watchpoint.exp has a test below which expects to see "Cannot
access memory at address 0x0" when a null pointer is dereferenced.

    gdb_test "watch -location nullptr->p->x" \
	"Cannot access memory at address 0x0"

This assumption is not true when the target is no-mmu, so we get

watch -location nullptr->p->x
Hardware watchpoint 28: -location nullptr->p->x
(gdb) FAIL: gdb.base/watchpoint.exp: watch -location nullptr->p->x

This patch is to check whether null pointer can be dereferenced first
and then do the test.

gdb/testsuite:

2014-06-01  Yao Qi  <yao@codesourcery.com>

	* gdb.base/watchpoint.exp (test_watch_location): Check null
	pointer can be dereferenced.  If not, do the test, otherwise
	skip it.
2014-06-01  Ray Donnelly  <mingw.android@gmail.com>

	* pex-win32.c (argv_to_cmdline): Don't quote
	args unnecessarily.
guile: Allow compilation with Guile <= 2.0.5.

gdb/
2014-06-01  Ludovic Courtès  <ludo@gnu.org>

	* configure.ac: When Guile is available, check for the
	availability of 'scm_new_smob'.
	* configure, config.h.in: Regenerate.
	* guile/guile-internal.h (scm_new_smob) [!HAVE_SCM_NEW_SMOB]: New
	function.
Fix PowerPC64 ELFv2 icf_safe failures

ELFv2 doesn't use .opd, so folding function code can't be allowed
in safe mode if a function's address might be taken.

	* powerpc.cc (Target_powerpc::local_reloc_may_be_function_pointer):
	Only ignore relocs on ELFv1.
	(Target_powerpc::global_reloc_may_be_function_pointer): Likewise.
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