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.
* standard library knows if it is linking against libc and will
sometimes call libc functions in that case instead of providing
redundant definitions
* fix infinite loop bug when resolving use declarations
* allow calling the same C function from different C imports.
closes#277
* push more logic from compiler to std/bootstrap.zig
* standard library provides way to access errno
closes#274
* fix compile error in standard library for windows
* add implementation of getRandomBytes for windows
