(MESS) sms.c: Several timing fixes:  [Enik Land]
- Fix flicker on Choplifter title screen by drawing the borders through timers.
- Instead trigger NMI at end of the display, do it at end of top border (line 261 after start of active screen area).
- Add a delay to NMI, to be later than HINT, as stated by Flubba's VDPTest readme.
- Also based on VDPTest readme, change VINT and Sprite Overflow flags to be later than VCount change.
- Delay a little the display callback, to fix the title scrolling of Road Rash (SMS game).
- Fixed documentation of the scanline sections and change some timings to match.
- Calculate initial VCount values, instead use of hardcoded values.