i386.md: Global update to use new string syntax where it will improve readability.

i386.md: Global update to use new string syntax where it will improve readability.

	* config/i386/i386.md: Global update to use new string syntax
	where it will improve readability.  Warning fixes:
	(*truncdfsf2_2): Abort if which_alternative is not 0 or 1.
	(*adddi_1_rex64, *adddi_2_rex64, *adddi_3_rex64,
	*adddi_4_rex64, *adddi_5_rex64): Cast 1 to unsigned int.

	* read-rtl.c: Syntactic sugar for C embedded in strings in
	machine descriptions.
	(read_string): Break inner loop into separate function.  Takes
	an int.  Dispatch to read_quoted_string or read_braced_string
	as appropriate.  Automatically insert a leading star on braced
	strings if STAR_IF_BRACED is true.
	(read_quoted_string, read_braced_string): New functions.
	* doc/rtl.texi, doc/md.texi: Document new syntax.  Update
	examples to match.

	* rtl.c: Split RTL reader (read_rtx, read_skip_spaces,
	traverse_md_constants, fatal_with_file_and_line,
	fatal_expected_char, read_name, read_string, def_hash,
	def_name_eq_p, read_constants, and related data) to its own
	file.  Weed out now-unnecessary #includes.
	* read-rtl.c: New file.
	* Makefile.in (HOST_RTL): Add read-rtl.o.
	(read-rtl.o): New rule.
	(rtl.o, $(HOST_PREFIX_1)rtl.o): Update dependencies.
	* doc/gcc.texi (Passes): Talk briefly about the support
	library used by genfoo.
	* doc/rtl.texi (Reading RTL): read_rtx is not available in the
	compiler itself.

From-SVN: r43646