[map] reduce/optimize iteration and mask.

[assyrianic]

https://github.com/assyrianic/Harbol/blob/883313f8544ef7b49bb70121e20c80a6e260e34f/map/map.c#L77

`(i = (i+1 >= mask)? ((i+1) & mask) : i+1)`
this is slower than just `i = ((i+1) & mask)`