tweaks: don't bother initializing freshly allocated multidata

After having been allocated, the multidata will get computed
immediately, in precalc_multicolorinfo() and draw_row(), so
first setting each element to -1 is a small waste of time.

src/color.c

@@ -235,9 +235,6 @@ void find_and_prime_applicable_syntax(void)
 void set_up_multicache(linestruct *line)
 {
 	line->multidata = nmalloc(openfile->syntax->nmultis * sizeof(short));
-
-	for (short index = 0; index < openfile->syntax->nmultis; index++)
-		line->multidata[index] = -1;
 }
 
 /* Determine whether the matches of multiline regexes are still the same,