Change references of .c files to .cc files

ChangeLog:

	* MAINTAINERS: Rename .c names to .cc.

contrib/ChangeLog:

	* filter-clang-warnings.py: Rename .c names to .cc.
	* gcc_update: Likewise.
	* paranoia.cc: Likewise.

contrib/header-tools/ChangeLog:

	* README: Rename .c names to .cc.

gcc/ChangeLog:

	* Makefile.in: Rename .c names to .cc.
	* alias.h: Likewise.
	* asan.cc: Likewise.
	* auto-profile.h: Likewise.
	* basic-block.h (struct basic_block_d): Likewise.
	* btfout.cc: Likewise.
	* builtins.cc (expand_builtin_longjmp): Likewise.
	(validate_arg): Likewise.
	(access_ref::offset_bounded): Likewise.
	* caller-save.cc (reg_restore_code): Likewise.
	(setup_save_areas): Likewise.
	* calls.cc (initialize_argument_information): Likewise.
	(expand_call): Likewise.
	(emit_library_call_value_1): Likewise.
	* cfg-flags.def (RTL): Likewise.
	(SIBCALL): Likewise.
	(CAN_FALLTHRU): Likewise.
	* cfganal.cc (post_order_compute): Likewise.
	* cfgcleanup.cc (try_simplify_condjump): Likewise.
	(merge_blocks_move_pred...