Prepare for formatting masks.

This is the version in Debian Jessie (oldstable).

Required according to RFC 3986:

> An implementation should accept uppercase letters as equivalent to
> lowercase in scheme names

Closes #330

This typo was present since the option was added in commit ed001e0c

`AllocatedPath::FromUTF8Throw()` will never return a nulled instance.

Don't use the bad `FatalError` library.

Let MainOrThrow() forward it to mpd_main().

Deinitialize the logging library after the last exception handler,
because that one could still need it.

Use `AtScopeExit()` to ensure it's always called, even if an exception
was thrown.