gccrs: macros: Handle matchers properly in repetitions

gccrs: macros: Handle matchers properly in repetitions

gcc/rust/ChangeLog:

	* expand/rust-macro-expand.cc (MacroExpander::match_matcher): Handle
	fragments differently based on whether or not we are currently trying
	to match a matcher in a repetition context.
	(MacroExpander::match_n_matches): Use new `in_repetition` argument
	properly when calling `match_matcher`.
	* expand/rust-macro-expand.h (MacroExpander::match_matcher): Allow
	passing extra `in_repetition` bool argument

gcc/testsuite/ChangeLog:

	* rust/compile/macro43.rs: New test.