c++: ICE on enum with bool value [PR99968]

BOOLEAN_TYPE also counts as integral, so verify_type should allow it.

	PR c++/99968

gcc/ChangeLog:

	* tree.c (verify_type): Allow enumerator with BOOLEAN_TYPE.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/is_enum2.C: New test.