Initialize all bits of the GMAC clock register, add comments.
and a few more.
Canonicalize boolean result from test_and_set_bit.

Not actually semantically significant for any callers, but Linux
documentation insists it is important, so we'll follow suit.

Fixes last part of PR kern/48999.
few more.
Pull LUNA's framebuffer improvements by Kenji Aoyama from OpenBSD/luna88k.

http://marc.info/?l=openbsd-cvs&m=141199909120631&w=2
>> Use raster(logic) operation, or ROP, function on LUNA frame buffer.
>> It makes 4bpp wscons putchar ~20% faster.

This Makes 4bpp wscons putchar ~30% on LUNA-II.

Also use the similar ROP in 1bpp putchar and cursor functions
and the 1bpp putchar is also ~5% faster.
While here, reduce diffs from OpenBSD a bit.

Tested on all 1bpp/4bpp/8bpp framebuffers.