TYPO3 Core

Many editors automatically drop trailing whitespace on saving files. When creating patches, this leads to the white-space cleanup being in the same patches as the actual code changes.

So I've decided to do the cleanup now so future core patches will not have the whitespace cleanup in them.

That's the cleanup which I've done:
- drop trailing whitespace
- drop any whitespace after the closing ?>
- drop surplus blank lines above the ?> and above the class-closing } (not in all files, though)
- drop surplus blank lines around the XCLASS stuff at the bottom of classes
- in one case, fix a type: it's > its
in one case, add a missing space after the "if" in the XCLASS stuff

(issue imported from #M12039)