re PR preprocessor/57757 (CPP extra inserted whitespace needs to be reviewed for C++11 user-defined literals)

	PR preprocessor/57757
	* lex.c (cpp_avoid_paste): Avoid pasting CPP_{,W,UTF8}STRING
	or CPP_STRING{16,32} with CPP_NAME or SPELL_LITERAL token that
	starts if a-zA-Z_.

	* g++.dg/cpp/paste1.C: New test.
	* g++.dg/cpp/paste2.C: New test.

From-SVN: r200875