Sync libiberty sources with gcc mainline.

Sync libiberty sources with gcc mainline.

2016-09-19  Andrew Stubbs  <ams@codesourcery.com>

	* pex-win32.c (argv_to_cmdline): Quote zero-length parameters.
	* testsuite/test-pexecute.c (main): Insert check for zero-length parameters.

2016-09-10  Mark Wielaard  <mjw@redhat.com>

	* cp-demangle.c (d_substitution): Change struct demangle_component
	variable name from c to dc.

2016-08-12  Marek Polacek  <polacek@redhat.com>

	PR c/7652
	* cp-demangle.c (d_print_mod): Add FALLTHRU.

2016-08-04  Marcel B?hme  <boehme.marcel@gmail.com>

	PR c++/71696
	* cplus-dem.c: Prevent infinite recursion when there is a cycle
	in the referencing of remembered mangled types.
	(work_stuff): New stack to keep track of the remembered mangled
	types that are currently being processed.
	(push_processed_type): New method to push currently processed
	remembered type onto the stack.
	(pop_processed_type): New method to pop currently processed
	remembered type from the stack.
	(work_stuff_copy_to_from): Copy values of new variables.
	(delete_non_B_K_work_stuff): Free stack memory.
	(demangle_args): Push/Pop currently processed remembered type.
	(do_type): Do not demangle a cyclic reference and push/pop
	referenced remembered type.