c, c++: Add new value for vector types for __builtin_classify_type

c, c++: Add new value for vector types for __builtin_classify_type

While filing a clang request to return 18 on _BitInts for
__builtin_classify_type instead of -1 they return currently, I've
noticed that we return -1 for vector types.  Initially I wanted to change
behavior just for __builtin_classify_type (type) form, as that is new in
GCC 14 and we've returned for 20+ years -1 for __builtin_classify_type
on vector expressions, but I was convinved otherwise, so this changes
the behavior even for that and now returns 19.

2023-11-20  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* typeclass.h (enum type_class): Add vector_type_class.
	* builtins.cc (type_to_class): Return vector_type_class for
	VECTOR_TYPE.
	* doc/extend.texi (__builtin_classify_type): Mention bit-precise
	integer types and vector types.
gcc/testsuite/
	* c-c++-common/builtin-classify-type-1.c (main): Add tests for vector
	types.