* cpp.texi: Update for handling of charconsts.
	* cpplex.c (maybe_read_ucs): Don't accept D800-DFFF.  Update
	diagnostics.  Skip to the end if the UCS is too short.
	(cpp_interpret_charconst): Long charconsts issue a warning
	not an error.

	* gcc.dg/cpp/charconst.c: New tests.
	* gcc.dg/cpp/escape.c: New tests.
	* gcc.dg/cpp/escape-1.c: New tests.
	* gcc.dg/cpp/escape-2.c: New tests.
	* gcc.dg/cpp/ucs.c: New tests.

From-SVN: r42514