PR c++/91979 - mangling nullptr expression

PR c++/91979 - mangling nullptr expression

2019-11-04  Kamlesh Kumar  <kamleshbhalui@gmail.com>

gcc/cp
        * cp/mangle.c (write_template_arg_literal): Handle nullptr
        mangling.
gcc
	* common.opt (-fabi-version): Document =14.
	* doc/invoke.texi (C++ Dialect Options): Likewise.
gcc/c-family
        * c-opts.c (c_common_post_options): Update
        latest_abi_version.
libiberty
        * cp-demangle.c (d_expr_primary): Handle
        nullptr demangling.
        * testsuite/demangle-expected: Added test.

From-SVN: r277801