repatch: Use NextEntryOffset to advance the buffer and to fix a crash on Wine.

Eh...?!? Apparently, the "DWORD-aligned" part in MSDN's documentation of ReadDirectoryChangesW() made me distrust the NextEntryOffset member of the FILE_NOTIFY_INFORMATION structure completely. (I blame Windows dialog patching, the DWORD alignment there was annoying enough.) As a result, I rolled my own pointer addition that was guaranteed to be DWORD-aligned...

... which then fails on Wine, which *doesn't* DWORD-align the individual FILE_NOTIFY_INFORMATION structure. This in turn crashes thcrap on change notifications of files with an odd file name length.