c++: Make *_cast<*> parsing more robust to errors [PR108438]

c++: Make *_cast<*> parsing more robust to errors [PR108438]

We ICE upon the following when trying to emit a -Wlogical-not-parentheses
warning:

=== cut here ===
template <typename T> T foo (T arg, T& ref, T* ptr) {
  int a = 1;
  return static_cast<T!>(a);
}
=== cut here ===

This patch makes *_cast<*> parsing more robust by skipping to the closing '>'
upon error in the target type.

Successfully tested on x86_64-pc-linux-gnu.

	PR c++/108438

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_postfix_expression): Use
	cp_parser_require_end_of_template_parameter_list to skip to the closing
	'>' upon error parsing the target type of *_cast<*> expressions.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/crash75.C: New test.