Constrained by having to work off the stack: no global variables, no static
variables.

System calls rewritten in SPARC assembly for minimum instruction count.
extern errno can't exist because of the restriction on working off stack.

crt0.o rewritten to provide code with PC of entry point.  Also instead of
calling exit(), as crt0.o does, it jumps to real entry point.

it would be nice to have a better way of doing the "implanter" program.
