next-line advancing two lines.

[Jason Rumney]

Since updating from CVS today, next-line and previous-line are moving 
two lines at a time inside certain source files once the cursor is past 
the initial comment block. This appears to be triggered by loading ECB 
(http://ecb.sourceforge.net). I can reproduce it by the following:

emacs -q --no-site-file

M-: (require 'ecb)
C-x C-f emacs/lisp/abbrev.el
C-s Code:
C-n
C-n

The second C-n fails.


Note that ecb only needs to be loaded, not activated for the bug to show 
itself. I have Cc'ed Klaus Berndl, the maintainer of ECB, as he may know 
what side-effects merely loading ECB has, so we can come up with a 
simpler test case.