Before:
* << is left shift, not allowed to shift 1 bits out
* <<% is left shift, allowed to shift 1 bits out
* >> is right shift, allowed to shift 1 bits out
After:
* << is left shift, allowed to shift 1 bits out
* >> is right shift, allowed to shift 1 bits out
* @shlExact is left shift, not allowed to shift 1 bits out
* @shrExact is right shift, not allowed to shift 1 bits out
Closes#413
* add `@divTrunc` and `@divFloor` functions
* add `@rem` and `@mod` functions
* add compile error for `/` and `%` with signed integers
* add `.bit_count` for float primitive types
closes#217