Fixed bitfield unshifted masking-out logic
Don't need to zero bitfields - this was a mask issue
Moved bitfield tests
Backend uses unsigned long longs too
Added 'l' length modifier to printf
Added bitfield initial padding test
_Bools aren't signed
Fixes for adjacent bitfield overflow
Bitfield init test/todo (empty fields need skipped, etc)
Changed cast logic to match new -1UL/CHAR_BIT code

Changed commented cast logic too - not implementing due to
signed/unsigned difference.
x86_64 support for loading 64-bit literals
Test case for ICE when loading casted 64-bit literal