Fix LookupColor

Using strncasecmp(3) with the lenght of the user-supplied colour name
will result in a false positive when the db key starts out with the
same string.

Eg, blue will also match BlueViolet (aka blue violet).

Since the shorter strings occur first in the database, avoid such
errors by treating a 0 result from strncasecmp(3) as a positive result
when the key’s length is longer than the supplied string’s.

os/oscolor.c

@@ -1590,6 +1590,8 @@ OsLookupColor(int		screen,
 	mid = (low + high) / 2;
 	c = &BuiltinColors[mid];
 	r = strncasecmp (&BuiltinColorNames[c->name], name, len);
+	if (r == 0 && strlen (&BuiltinColorNames[c->name]) > len)
+	    r++;
 	if (r == 0)
 	{
 	    *pred = c->red * 0x101;