Fix up implementations to ensure they dispose any stream they acquire, and ensure the constructor will not leave a stream open if it fails. Dispose folders when unmounting them in GlobalFileSystem.
- Almost all calls to Stream.Read were broken. These have been patched to all go through ReadBytes which itself has been fixed to function correctly. The key thing to note is that Stream.Read is very much allowed to return less than the requested number of bytes. If this happens and you're not checking the return result, you'll be working with partially initialized arrays and really bad stuff happens when you do that.
- Call CopyTo rather than copying between streams manually.
- Peek and ReadUInt8 have been changed to avoid a pointless array allocation which is significant overhead for such simple calls.
- Made private methods static where possible (runtime can elide checking the object for null).
- Declared attribute classes as sealed (allows reflection on attributes to complete faster).
- Moved some static cctor's into field initializers (static cctor's are slower than static field initializers).
- Made classes static if they contained only static methods (can't create instances of useless objects).
- Use inferable Exts.Lazy and not new Lazy<T>().
- Added required STAThread attribute to CrashDialog.
- Removed unused parameters in private methods.
- Added Serializable attribute to exceptions.
- Added parameter name in calls to ArgumentNullException.
- Use of as operator instead of is + cast.
- Changed (x as Foo).Bar anti-pattern into ((Foo)x).Bar. Results in sensible cast exceptions on error rather than null dereferences.
- Removed unused method in NullShader.
