Sync libiberty with upstream GCC.

include/ChangeLog
	* libiberty.h (PEX_STDOUT_APPEND): New flag.
	(PEX_STDERR_APPEND): Likewise.

	* demangle.h (DMGL_DLANG): New macro.
	(DMGL_STYLE_MASK): Add DMGL_DLANG.
	(demangling_styles): Add dlang_demangling.
	(DLANG_DEMANGLING_STYLE_STRING): New macro.
	(DLANG_DEMANGLING): New macro.
	(dlang_demangle): New prototype.

	* longlong.h: Add __udiv_w_sdiv prototype.

libiberty/ChangeLog
	* cp-demangle.c (d_substitution): Handle abi tags on abbreviation.

	* pex-common.h (struct pex_funcs): Add new parameter for open_write field.
	* pex-unix.c (pex_unix_open_write): Add support for new parameter.
	* pex-djgpp.c (pex_djgpp_open_write): Likewise.
	* pex-win32.c (pex_win32_open_write): Likewise.
	* pex-common.c (pex_run_in_environment): Likewise.

	* Makefile.in (CFILES): Add d-demangle.c.
	(REQUIRED_OFILES): Add d-demangle.o.
	* cplus-dem.c (libiberty_demanglers): Add dlang_demangling case.
	(cplus_demangle): Likewise.
	* d-demangle.c: New file.
	* testsuite/Makefile.in (really-check): Add check-d-demangle.
	* testsuite/d-demangle-expected: New file.

	* simple-object-elf.c (simple_object_elf_write_ehdr): Correctly
	handle objects with more than SHN_LORESERVE sections.
	(simple_object_elf_write_shdr): Add sh_link parameter.
	(simple_object_elf_write_to_file): Correctly handle objects with
	more than SHN_LORESERVE sections.

	* cp-demangle.c (d_dump): Only access field from s_fixed part of
	the union for DEMANGLE_COMPONENT_FIXED_TYPE.
	(d_count_templates_scopes): Likewise.

	* testsuite/demangler-fuzzer.c: New file.
	* testsuite/Makefile.in (fuzz-demangler): New rule.
	(demangler-fuzzer): Likewise.
	(mostlyclean): Clean up demangler fuzzer.
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