tree: Handle BITINT_TYPE in type_contains_placeholder_1 [PR112511]

tree: Handle BITINT_TYPE in type_contains_placeholder_1 [PR112511]

The following testcase ICEs because BITINT_TYPE isn't handled in
type_contains_placeholder_1.  Given that Ada doesn't emit it, it doesn't
matter that much where exactly we handle it as right now it should never
contain a placeholder; I've picked the same spot as INTEGER_TYPE, but if
you prefer e.g. the one with OFFSET_TYPE above, I can move it there too.

2023-11-14  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/112511
	* tree.cc (type_contains_placeholder_1): Handle BITINT_TYPE like
	INTEGER_TYPE.

	* gcc.dg/pr112511.c: New test.