Minor documentation improvements.

git-svn-id: http://lufa-lib.googlecode.com/svn@2664 d5102386-fcda-11dd-9fdb-3debd5008f28
Fixed race condition in the DFU class bootloader causing failed device reprogramming in some circumstances (thanks to Luis Mendes).

git-svn-id: http://lufa-lib.googlecode.com/svn@2665 d5102386-fcda-11dd-9fdb-3debd5008f28