[NTVDM]: Make static some variables, fix IRQ1/12 timing, use NT QueryPerformanceCounter API instead of its Win32 part and move the "while (VdmRunning && CpuRunning)" loop into ClockUpdate.

git-svn-id: svn://svn.reactos.org/reactos/trunk/reactos@65377 97493ccd-5924-5043-b1f5-66cb403b36ce
[NTVDM]
- Store in bit 7 of Bda->VGAOptions (40:87) whether we needed to clear video memory (or not) when changing the video mode.
- When retrieving the current video mode, set this bit 7 as required.
- Improve a bit the DPRINT of VidBiosSetVideoMode for diagnostic purposes.
- Remove the temporary "fix" (read: hack, and it broke some apps) from r65015 / r65018 : I'm working on a real fix.
- Rework some subfunctions of the INT 10h, AH=11h function (font generator).
- Fix reporting "256 kb video memory" in the Bda->VGAOptions flag.

git-svn-id: svn://svn.reactos.org/reactos/trunk/reactos@65379 97493ccd-5924-5043-b1f5-66cb403b36ce