Weirdly, I needed to sprinkle more parens here to get gcc-as in 6.4
to correctly generate things.
Without them, I'd get an unknown variable reference to SKEIN_ASM_UNROLL1024.
This at least links now, but I haven't run any test cases against it.
It may be worthwhile doing it in case gcc-as demands we liberally sprinkle
more brackets around variables in .if statements.
Thanks to ed for the suggestion of just sprinkling more brackets to
see if that helped.
Reviewed by: emaste
58958a74f2