VM: Remove redundant #ifdef FACTOR_DEBUGs

FACTOR_DEBUG checks around asserts aren't needed, since FACTOR_ASSERT is
already conditionally defined by FACTOR_DEBUG.
VM: Remove WINCE #ifndef; fold wince? words
VM: Replace u8-64, s8-64, cell, fixnum with stdint.h equivalents
VM: Fixup cast formatting after clang-format

clang-format doesn't recognize casts to non-pointer/non-template types
so it winds up adding a space between the right paren and the expression
and then failing to recognize prefix operators in the process
(e.g. foo = (cell) & bar; should be foo = (cell)&bar;). This commit
manually fixes up the major cases (fixnum, cell, all types ending in _t).