c1x-uni-string-1.c, [...]: New tests.

gcc/testsuite:
	* gcc.dg/c1x-uni-string-1.c, gcc.dg/c1x-uni-string-2.c: New tests.

libcpp:
	* include/cpplib.h (struct cpp_options): Add rliterals.
	* init.c  (struct lang_flags, lang_defaults): Add rliterals.
	(cpp_set_lang): Set rliterals option.
	(cpp_init_builtins): Define __STDC_UTF_16__ and __STDC_UTF_32__.
	* lex.c (_cpp_lex_direct): Only accept raw strings if rliterals.

From-SVN: r177868