Fix right & left shifts for all types, as well as <<= and >>=

Conflicts:
	Int128.xs
Changes for shift fixes
Make right shift for signed int128 consistent with int64

If shift >= 128, return 0 if shifted number >=0  and -1 otherwise
Ignore perl_math_int64.o
Sort .gitignore
More Changes updates
Merge pull request #6 from salva/dave/shift-fixes-alone

Make left/right shift return 0 for 128+ bit shift