Added the same open()/fopen()/creat()/mmap() -> sys_XXX calls.

Added the same open()/fopen()/creat()/mmap() -> sys_XXX calls.

Tidied up some of the mess (no other word for it). Still doesn't
compile cleanly. There are calls with incorrect parameters that
don't seem to be doing the right thing.

This code still needs surgery :-(.

Jeremy.
(This used to be commit 18ff93a9abbf68ee8c59c0af3e57c63e4a015dac)