Now that procfs.c is only ever used by Solaris, and, both x86 and
SPARC Solaris support watchpoints (*), we don't need the separate
procfs_use_watchpoints function. Getting rid of it simplifies
C++ification of target_ops.
(*) and I assume that any other Solaris port would use the same kernel
debug API interfaces for watchpoints. Otherwise, we can worry about
it if it ever happens.
gdb/ChangeLog:
2018-05-02 Pedro Alves <palves@redhat.com>