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
* add std.os.deleteTree
* add std.os.deleteDir
* add std.os.page_size
* add std.os API for iterating over directories
* refactor duplication in build.zig
* update documentation on how to run tests
* zig build system: create standard dynamic library sym links
* unwrapping an error results in a panic message that contains
the error name
* rename error.SysResources to error.SystemResources
* add std.os.symLink
* add std.os.deleteFile
* See #204 - zig build system
* allow builtin types Os, Environ, Arch to be used at runtime.
they have zero_bits=false and debug info now.
* Eradicate use of `@alloca` in std for syscalls. See #225
* add `std.io.writeFile`
* `std.debug.panic` adds a newline to format
* In-progress os.ChildProcess.spawn implementation. See #204
* Add explicit cast from integer to error. Closes#294
* fix casting from error to integer
* fix compiler crash when initializing variable to undefined
with no type
