#define bswap_32 bswap32 for NetBSD in the mach64 driver; also, for the
sis driver, use either NetBSD's atomic ops if we have them, else
check for gcc's __sync_synchronize.  I suppose the right thing to do is
split the dri drivers out of this package, but hopefully this will
resolve [pkg/39359].  No revision bump, as I just updated the package
a few hours ago.

(bjs)