Newline in raw string literals blow up macro expansion

Issue

A raw string literal should become a single pptoken before macros are expanded. GCC seems to disagree:

$ g++ --version
g++ (GCC) 4.7.0 20120507 (Red Hat 4.7.0-5)
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ rpm -qf `which g++`
devtoolset-1.0-gcc-c++-4.7.0-5.3.el5
$ cat raw_string_literal.cpp
#define STR(lit) lit

const char x[] = R"(
x)";
const char y[] = STR(R"(
x)");
$ g++ -std=c++11 raw_string_literal.cpp
raw_string_literal.cpp:5:22: error: unterminated raw string
raw_string_literal.cpp:5:1: error: stray 'R' in program
raw_string_literal.cpp:6:3: warning: missing terminating " character [enabled by default]
raw_string_literal.cpp:5:1: error: missing terminating " character
raw_string_literal.cpp:5:18: error: initializer fails to determine size of 'y'
raw_string_literal.cpp:5:18: error: expected ',' or ';' at end of input