Implement specification of MI tests as comments

	Implement specification of MI tests as comments
	in C and C++ sources.
	* lib/mi-support.exp (mi_autotest_data): New variable.
	(mi_autotest_source): New variable.
	(count_newlines, mi_prepare_inline_tests)
	(mi_get_inline_test, mi_continue_to_line)
	(mi_run_inline_test, mi_tbreak)
	(mi_send_resuming_command, mi_wait_for_stop): New functions.
	* gdb.mi/mi-var-cp.exp: Move most content to the C file.
	Run inline tests.
	* gdb.mi/mi-var-cp.cc: Define tests here.