The purpose of this is:
* Only one way to do things
* Changing a function with void return type to return a possible
error becomes a 1 character change, subtly encouraging
people to use errors.
See #632
Here are some imperfect sed commands for performing this update:
remove arrow:
```
sed -i 's/\(\bfn\b.*\)-> /\1/g' $(find . -name "*.zig")
```
add void:
```
sed -i 's/\(\bfn\b.*\))\s*{/\1) void {/g' $(find ../ -name "*.zig")
```
Some cleanup may be necessary, but this should do the bulk of the work.
* add u3, u4, u5, u6, u7 and i3, i4, i5, i6, i7
* shift operations shift amount parameter type is
integer with log2 bit width of other param
- This enforces not violating undefined behavior on
shift amount >= bit width with the type system
* clean up math.log, math.ln, math.log2, math.log10
closes#403
