Fix hyphenation command

At least, it doesn’t throw an error anymore. Todo: accept argument
that allows the user to select the language for the hyphenation
exception.
M: Fix hyphenation command

(from: release_2.0)
Allow hyphenation in compound words

This is especially useful für German texts where you have
longword-anotherlongword and TeX is so cool to prohibit
hyphenation in the second word :( 
So we insert a glue of width 0 to make a new word.