Old:
```
while (condition; expression) {}
```
New:
```
while (condition) : (expression) {}
```
This is in preparation to allow nullable and
error union types as the condition. See #357
See #329
Supporting work:
* move std.cstr.Buffer0 to std.buffer.Buffer
* add build.zig to example/shared_library/ and add an automated test
for it
* add std.list.List.resizeDown
* improve std.os.makePath
- no longer recursive
- takes into account . and ..
* add std.os.path.isAbsolute
* add std.os.path.resolve
* reimplement std.os.path.dirname
- no longer requires an allocator
- handles edge cases correctly
