Make local variables static.

Misc cleanup.

- move function declarations after struct declarations and
before global variables
- sort function declarations per actual implementation
- explicitly denote 'static' for static functions
- some KNF

No functional change (though gcc generates different binary).

branches: 1.1.2;
Add a support for gpx(4) color framebuffer found on VAXstation 3100.

Poted from OpenBSD/vax. Note smg(4) monochrome onboard framebuffer
driver is also changed attached only if gpx(4) is not installed
or flags 1 is specified in config files, as OpenBSD did.

Tested on my VAXstation 3100/m30 with and without 8bpp gpx(4).
Revied on port-vax@ and "Please go ahead!" from ragge@.
https://mail-index.netbsd.org/port-vax/2023/01/thread1.html#004147

Worth to pullup to netbsd-10.