quick fix for crash of completion on unknown words

git-svn-id: http://svn.code.sf.net/p/texstudio/code@4146 92cce386-e96d-4106-809f-596c673a3fd8
also check for uppercase PPC define

git-svn-id: http://svn.code.sf.net/p/texstudio/code@4147 92cce386-e96d-4106-809f-596c673a3fd8