Motivation:
`PlatformDependent#normalizedOs()` already caches normalized variant of
the value of `os.name` system property. Instead of inconsistently
normalizing it in every case, use the utility method.
Modifications:
- `PlatformDependent`: `isWindows0()` and `isOsx0()` use `NORMALIZED_OS`;
- `PlatformDependent#normalizeOs(String)` define `darwin` as `osx`;
- `OpenSsl#loadTcNative()` does not require `equalsIgnoreCase` bcz `os`
is already normalized;
- Epoll and KQueue: `Native#loadNativeLibrary()` use `normalizedOs()`;
- Use consistent `Locale.US` for lower case conversion of `os.name`;
- `MacOSDnsServerAddressStreamProvider#loadNativeLibrary()` uses
`PlatformDependent.isOsx()`;
Result:
Consistent approach for `os.name` parsing.
3ecb32357c