Eliminate an unuted function argument.

* vc.el, all backends: API simplification: Remove 4th 'default-state'
argument from vc-dir-status files and its backend methods - no backend
method ever set it.  It was used only in the fallback method to to set
a default of 'up-to-date, though a convoluted call chain obscured
this.
Fixes: debbugs:9133

* nsimage.m (initFromSkipXBM:width:height:flip:length:): Set bmRep
to nil after release.
Allow to search for characters whose bidi directionality was overridden.

 src/bidi.c (bidi_find_first_overridden): New function.
 src/xdisp.c (Fbidi_find_overridden_directionality): New function.
 (syms_of_xdisp): Defsubr it.
 src/dispextern.h (bidi_find_first_overridden): Add prototype.

 doc/lispref/display.texi (Bidirectional Display): Document
 'bidi-find-overridden-directionality'.

 etc/NEWS: Mention 'bidi-find-overridden-directionality'.