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.
This covers the majority of the functions as covered by the C99
specification for a math library.
Code is adapted primarily from musl libc, with the pow and standard
trigonometric functions adapted from the Go stdlib.
Changes:
- Remove assert expose in index and import as needed.
- Add float log function and merge with existing base 2 integer
implementation.
See https://github.com/tiehuis/zig-fmath.
See #374.
