changes to loadfilename & co. to make savesystem transparent to
 assertions and ~~

wordsets.fs: Added missing float words
Added 16 bit and 64 bit support in cross.fs
Fixed some bugs which asume sizeof(int)=sizeof(Cell)

in machine.h; threw out such hacks in engine.c for the 386.
renamed endian to bigendian

cstr is now a function that can process arbitrarily long strings