gccrs: Add clarity to the code

gccrs: Add clarity to the code

Use an enum instead of bool to check if a comment is internal, use good
include and replace some variable name.

gcc/rust/ChangeLog:

	* ast/rust-ast-collector.cc (TokenCollector::begin_internal_comment):
	Change a boolean with an enum.
	(TokenCollector::end_internal_comment): Likewise.
	* ast/rust-ast-collector.h: Likewise + change include.
	* ast/rust-ast-dump.cc (Dump::Dump): Change variable name.
	* ast/rust-ast-dump.h: Likewise + replace vector with a set.
	* rust-session-manager.cc (Session::enable_dump): Change variable
	name.
	(Session::handle_internal_blacklist): Change function name.
	(Session::handle_excluded_node): Likewise.
	(Session::dump_ast_pretty_internal): Change vector with a set.
	* rust-session-manager.h (struct CompileOptions): Likewise + change
	variable name.

Signed-off-by: Benjamin Thos <benjamin.thos@epita.fr>