Basic: restore {,u}intptr_t on NetBSD/ARM

NetBSD uses `long int` for `intptr_t` on ARM.  This was changed in SVN
r316046, referenced against other compilers.  However, NetBSD's
reference was incorrect as the current clang behaviour is more
up-to-date.  Restore the original behaviour for that target.

llvm-svn: 316204