internal defines: while allowed to be syntactically interspersed with
non-defines, behave as if all the defines were at the top of the begin!
This needs fixing before some nasty-to-find bugs creep in.

r! in the debugger will cause errors if it returns to the non-top stack
frame, because of the global stack. This really needs fixing...

Binary+ and multi-arg + (also -, *, /, ...)

Unix fork

Nonblocking threads!

Gethomedirectory functions

File stating and and other file io ops.
