core cleanups and fixes...

macro: new_pc[0]=x --> NEW_PC(x)
macro: cycle[0]=x CYCLES(X)
improvements on CORE_FAST_CORE_DIFF_TRACE output.
added some documentation of option flags.
use of common data reference on some register access operations.
changes to allow core to operate local to project.
global uflash access option.
asr: calculate and use common negative result across flags.
moved a few bit shifts earlier in some functions, to reduce a few
	redundant operations.
std_std: operation fixes.
avr_core_run_many: tightened up the code a bit.
sim_fast_core_init: added to enable use local to project.

	modified:   simavr/sim/sim_fast_core.c