6.0pre3

Added the cpm platform. Made some optimisations to the i80 code generator,
including getting topgen up and running and adding some peephole optimiser
rules. Fixed loads of bugs in ego so that it now works on platforms that
support it (pc86 and linux386). Made the floating point work on platforms
that support it (pc86 and linux386 again). Made stdint.h work. Lots and lots
of bugfixes and tweaks everywhere.