Change syscall reg ordering to match conv. order

Also add some defines
Add crt0
Make syscall interface less annoying

Use inline funcs instead of macros
Make file reread error check explicit
Remove stale comments
Cosmetic fixes for naming standard
minor func ordering pref
Wait sets exit status
Raise user program size to 32k

Also build as elf and preinitialize bss in flat image
Use fresh process image every time

previously recycling bss area
Change heap extend interface to sbrk

Easier libc porting

userspace malloc unlocked
Fix bug in user prog