i#4226: Faster fragment deletion event
Adds a dedicated loop to call the fragment deletion event without calling all the other fragment freeing code. This speeds up detach and process exit in general by 2x.
Tested performance and correctness on a third-party app; also tested correctness on a hacked drwrap-detach-test to ensure the same number of deletion event calls were made. I don't think it's easy to make a performance regression test unfortunately.
Fixes #4226 (closed)