Port rasops'fied smg(4) framebuffer driver for VS3100 from OpenBSD/vax.

This allows using more fonts other than 8x15 pixels on smg(4).
Tested on my VAXstation 3100/m30.

Note the bitorder of smg(4) VRAM is LSB first (i.e. LSBit is the
most left side pixel) and this requires more complicated changes
to bitmask ops in MI rasops(9) because several LE machines have
VRAMs whose MSBit is connected to the most left side pixel,
but for now I prepared smg(4) specific putchar and cursor ops
based on old luna68k omrasops.