patch 8.1.0680: not easy to see what features are unavailable

Problem:    Not easy to see what features are unavailable.
Solution:   Highlight disabled features in the :version output. (Nazri Ramliy,
            closes #3756)
diff --git a/src/version.c b/src/version.c
index 2571a8c..8dcd56f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    680,
+/**/
     679,
 /**/
     678,
@@ -2266,6 +2268,9 @@
     int		nrow;
     int		item_count = 0;
     int		width = 0;
+#ifdef FEAT_SYN_HL
+    int		use_highlight = (items == (char_u **)features);
+#endif
 
     /* Find the length of the longest item, use that + 1 as the column
      * width. */
@@ -2307,7 +2312,12 @@
 
 	    if (idx == current)
 		msg_putchar('[');
-	    msg_puts(items[idx]);
+#ifdef FEAT_SYN_HL
+	    if (use_highlight && items[idx][0] == '-')
+		msg_puts_attr(items[idx], HL_ATTR(HLF_W));
+	    else
+#endif
+		msg_puts(items[idx]);
 	    if (idx == current)
 		msg_putchar(']');
 	    if (last_col)