gcov-profile/114715 - missing coverage for switch

gcov-profile/114715 - missing coverage for switch

The following avoids missing coverage for the line of a switch statement
which happens when gimplification emits a BIND_EXPR wrapping the switch
as that prevents us from setting locations on the containing statements
via annotate_all_with_location.  Instead set the location of the GIMPLE
switch directly.

	PR gcov-profile/114715
	* gimplify.cc (gimplify_switch_expr): Set the location of the
	GIMPLE switch.

	* gcc.misc-tests/gcov-24.c: New testcase.