move memory model definition into low-level memory.py
add --map-drives to test.sh so that paths outside the cwd's tree can be used again
no greeting if loading program, also from positional argument
use fre() in greeting rather than var.total_mem
adjust data memory map with file 0 fcb to match gwbasic memory size for non-default /f and /s
fix references to field_mem globals (now in memory.py)
implement VARPTR(#1) for file numbers
clear TODO: implement VARPTR(#1) for file numbers
bring program_memory_start in line with memory.code_start
implement stack size switch in CLEAR
implement CLEAR: set total data memory size
update HELP for newly implemented CLEAR arguments
allow (but ignore) -i option (GWBASIC /i seems to have no effect)
implement max-memory option (GWBASIC /m)
implement PEEK into program code
allow POKE into code space when --allow-code-poke is specified
remove default options from PCBASIC.INI, use builtin defaults instead
Merge branch 'master' into topic-memory
reset variables & memory model on startup load. pass CHAINMEM test.
allow changing of reserved memory size to match BASICA, Tandy, PCjr free memory values