Timing functions delay_ms, delay_us and delay_ticks now use Timer B.

Timing functions delay_ms, delay_us and delay_ticks now use Timer B.

This has been verified with a GF31 board (hence x2274 chip) and
read/write/erase and dev ID extraction on dsPIC33FJ128GP710 and
PIC24FJ64GA002 chips.

Use of Timer B should work as specified on GF1x boards (hence
msp430f161x chips) based on my (cursory) review of the MSP430x1xx
family "user's guide." However note that this has still NOT been
tested on hardware.

git-svn-id: https://svn.code.sf.net/p/goodfet/code/trunk@643 12e2690d-a6be-4b82-a7b7-67c4a43b65c8