updated for version 7.4.284
Problem:    Setting 'langmap' in the modeline can cause trouble.  E.g. mapping
	    ":" breaks many commands. (Jens-Wolfhard Schicke-Uffmann)
Solution:   Disallow setting 'langmap' from the modeline.
Added tag v7-4-284 for changeset 3c35ca9666e8