MFbed: Update the German documentation set.

doc/de_DE.ISO8859-1/books/handbook/Makefile 1.104 -> 1.105
doc/de_DE.ISO8859-1/books/handbook/disks/chapter.sgml 1.273 -> 1.274
doc/de_DE.ISO8859-1/books/handbook/install/chapter.sgml 1.347 -> 1.349
doc/de_DE.ISO8859-1/books/handbook/x11/chapter.sgml 1.179 -> 1.180

Obtained from: The FreeBSD German Documentation Project.