Operator precedence gets messed up when using bitwise operators on bitlib mode

[Lyrth]

There are no operator precedence rules followed when transforming bitwise operations into bitlib function calls when using --bitwise library or equivalent. The below code

print( ~2 & a == 4 * b )

will be compiled into

print(bit.bnot(bit.band(2, a==4*b)));

which would be wrong.

[Maiori44]

since this can be avoided by using ()s, I'll fix it for 4.0 rather than do a patch.