gccrs: Fix issue with parsing unsafe block expression statements

gcc/rust/ChangeLog:

	* parse/rust-parse-impl.h
	(Parser::parse_stmt): Handle unsafe expression statements.

gcc/testsuite/ChangeLog:

	* rust/compile/issue-1422.rs: New test.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>