* c-common.c (combine_strings): Also set TREE_READONLY.
	Change warn_write_strings to flag_const_strings.
	* c-decl.c, c-tree.h: Likewise.
cp/
	* tree.c (lvalue_type): Fix for arrays.
	* typeck.c (string_conv_p): New fn.
	(convert_for_assignment): Use it.
	(build_unary_op): Use lvalue_type.
	* call.c (standard_conversion, convert_like): Use string_conv_p.
	(add_function_candidate): Use lvalue_type.
	* cvt.c (convert_to_reference): Likewise.
	* decl2.c (lang_decode_option): Ignore -traditional.
	* decl.c (init_decl_processing): flag_writable_strings inhibits
	flag_const_strings.
	* lang-options.h (lang_options): Add fconst-strings to the list
	of valid options.
	* decl2.c (lang_f_options, lang_decode_option): Likewise.

From-SVN: r21928