Fix internal error on broken import of vector intrinsics
The change also makes small adjustments to warning messages for intrinsics.
gcc/ada/
* gcc-interface/decl.c (gnat_to_gnu_subprog_type): Turn variable
into constant. Capitalize GCC in warning message.
(intrin_arglists_compatible_p): Change parameter to pointer-to-const
Adjust warning messages. Turn warning into error for vector types.
(intrin_return_compatible_p): Likewise.
(intrin_profiles_compatible_p): Change parameter to pointer-to-const