gccrs: Implement initial pattern analysis pass.

gccrs: Implement initial pattern analysis pass.

gcc/rust/ChangeLog:

	* Make-lang.in: Add rust-hir-pattern-analysis.o.
	* rust-session-manager.cc (Session::compile_crate):
		Add pattern analysis pass.
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::visit):
		Do typecheck for subpatterns.
	* checks/errors/rust-hir-pattern-analysis.cc: New file.
	* checks/errors/rust-hir-pattern-analysis.h: New file.

gcc/testsuite/ChangeLog:

	* rust/compile/exhaustiveness1.rs: New test.
	* rust/compile/exhaustiveness2.rs: New test.
	* rust/compile/exhaustiveness3.rs: New test.

Signed-off-by: Raiki Tamura <tamaron1203@gmail.com>