* 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
