Allow for native compiling .el.gz files

Allow for native compiling .el.gz files

This is needed for installed instances compiled with NATIVE_FAST_BOOT

	* src/comp.c (maybe_defer_native_compilation): Search for .el.gz
	too as a source if the .el is not found.
	(Fcomp_el_to_eln_filename): Remove the .gz in case to
	generate the hash.

	* lisp/emacs-lisp/comp.el (comp-valid-source-re): New defconst.
	(comp-run-async-workers, native-compile-async): Make use of
	`comp-valid-source-re'.