Issue Description:

decomposedStringWithCompatibilityMapping() appears to do nothing if called near the beginning of program execution.

Certain other APIs seem to trigger as a side‐effect whatever initial loading is necessary for normalization to work correctly. At least `XCTMain` and `Locale.current` fall in this category. If either has already been touched, the problem does not seem to manifest itself.

A reproducible example is already outlined on the forums.