libffi: Integrate build with GCC

1. Integrate with GCC build.
2. Disable static trampolines by default.
3. Support multilib.

	* Makefile.am (AUTOMAKE_OPTIONS): Add info-in-builddir.
	(ACLOCAL_AMFLAGS): Set to -I .. -I ../config.
	(SUBDIRS): Don't add doc.
	(TEXINFO_TEX): New.
	(MAKEINFOFLAGS): Likewise.
	(info_TEXINFOS): Likewise.
	(STAMP_GENINSRC): Likewise.
	(STAMP_BUILD_INFO): Likewise.
	(all-local): Likewise.
	(stamp-geninsrc): Likewise.
	(doc/libffi.info): Likewise.
	(stamp-build-info:): Likewise.
	(CLEANFILES): Likewise.
	(MAINTAINERCLEANFILES): Likewise.
	(AM_MAKEFLAGS): Likewise.
	(all-recursive): Likewise.
	(install-recursive): Likewise.
	(mostlyclean-recursive): Likewise.
	(clean-recursive): Likewise.
	(distclean-recursive): Likewise.
	(maintainer-clean-recursive): Likewise.
	(LTLDFLAGS): Replace libtool-ldflags with ../libtool-ldflags.
	(AM_CFLAGS): Add -g -fexceptions.
	(libffi.map-sun): Replace make_sunver.pl with
	../contrib/make_sunver.pl.
	(dist-hook): Removed.
	Include $(top_srcdir)/../multilib.am.
	* configure.ac: Add AM_ENABLE_MULTILIB.
	Remove the frv*-elf check.
	(AX_ENABLE_BUILDDIR): Removed.
	(AM_INIT_AUTOMAKE): Add [no-dist].
	Add --enable-generated-files-in-srcdir.
	(C_CONFIG_MACRO_DIR): Removed.
	(AX_COMPILER_VENDOR): Likewise.
	(AX_CC_MAXOPT): Likewise.
	(AX_CFLAGS_WARN_ALL): Likewise.
	Remove the GCC check.
	(SYMBOL_UNDERSCORE): Removed.
	(AX_CHECK_COMPILE_FLAG): Likewise.
	Remove --disable-docs.
	(ACX_CHECK_PROG_VER): Check makeinfo.
	(BUILD_DOCS): Updated.
	(exec-static-tramp): Don't enable use of static exec trampolines
	by default.
	Remove --disable-multi-os-directory.
	(GCC_WITH_TOOLEXECLIBDIR): New.
	Support cross host.
	Support --enable-multilib.
	* include/Makefile.am (nodist_include_HEADERS): Removed.
	(gcc_version): New.
	(toollibffidir): Likewise.
	(toollibffi_HEADERS): Likewise.
	* Makefile.in: Regenerate.
	(GCC_BASE_VER): New.
	(AC_CONFIG_FILES): Remove doc/Makefile.
	(AC_CONFIG_LINKS): New.
	* aclocal.m4: Likewise.
	* configure: Likewise.
	* fficonfig.h.in: Likewise.
	* mdate-sh: Likewise.
	* include/Makefile.in: Likewise.
	* man/Makefile.in: Likewise.
	* testsuite/Makefile.in: Likewise.