Fix several crashes of C++ demangler on fuzzed input.

libiberty/
	* cp-demangle.c (d_dump): Fix syntax error.
	(d_identifier): Adjust type of len to match d_source_name.
	(d_expression_1): Fix out-of-bounds access.  Check code variable for
	NULL before dereferencing it.
	(d_find_pack): Do not recurse for FIXED_TYPE, DEFAULT_ARG and NUMBER.
	(d_print_comp_inner): Add NULL pointer check.
	* cp-demangle.h (d_peek_next_char): Define as inline function when
	CHECK_DEMANGLER is defined.
	(d_advance): Likewise.
	* testsuite/demangle-expected: Add new testcases.

From-SVN: r225727