Before, if you did something like:
```
const hi1 = "hi";
const hi2 = hi1;
```
This would create the "hi" data twice in the built object.
But since the value is const we don't have to duplicate the
data, now we take advantage of this fact.
closes#336
Old:
```
while (condition; expression) {}
```
New:
```
while (condition) : (expression) {}
```
This is in preparation to allow nullable and
error union types as the condition. See #357
* add ability to add assembly files when building an exe, obj, or lib
* add implicit cast from `[N]T` to `?[]const T` (closes#343)
* remove link_exe and link_lib in favor of allowing build_exe and
build_lib support no root zig source file
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
Andrew Kelley