One more warning about using an uninitialized field

[Dmitry Antipov <dmantipov@yandex.ru>]

One more warning about using an uninitialized field, now BIDI-related:

==11279== Conditional jump or move depends on uninitialised value(s)
==11279==    at 0x443145: compute_display_string_pos (xdisp.c:3582)
==11279==    by 0x500D93: bidi_fetch_char (bidi.c:953)
==11279==    by 0x501FF9: bidi_paragraph_init (bidi.c:1299)
==11279==    by 0x47AEAE: Fcurrent_bidi_paragraph_direction (xdisp.c:20419)

 From xdisp.c:

   3579    if (charpos >= eob
   3580        /* We don't support display properties whose values are strings
   3581           that have display string properties.  */
! 3582        || string->from_disp_str
   3583        /* C strings cannot have display properties.  */
   3584        || (string->s && !STRINGP (object)))
   3585      {
   3586        *disp_prop = 0;
   3587        return eob;
   3588      }

I don't know how critical it may be, but please consider the following precaution:

=== modified file 'src/xdisp.c'
--- src/xdisp.c	2014-01-13 11:30:30 +0000
+++ src/xdisp.c	2014-01-23 08:53:41 +0000
@@ -6409,6 +6409,7 @@
        it->bidi_it.string.s = NULL;
        it->bidi_it.string.lstring = Qnil;
        it->bidi_it.string.bufpos = 0;
+      it->bidi_it.string.from_disp_str = 0;
        it->bidi_it.string.unibyte = 0;
        it->bidi_it.w = it->w;
      }
@@ -20411,6 +20412,7 @@
        itb.string.s = NULL;
        itb.string.lstring = Qnil;
        itb.string.bufpos = 0;
+      itb.string.from_disp_str = 0;
        itb.string.unibyte = 0;
        /* We have no window to use here for ignoring window-specific
  	 overlays.  Using NULL for window pointer will cause

Dmitry