patch 8.0.1362: terminal window colors wrong when using Terminal highlighting

Problem:    Terminal window colors wrong when using Terminal highlighting.
Solution:   Set ansi_index when setting the default color.  Also cache the
            color index for Terminal. (Ozaki Kiichi, closes #2393)
diff --git a/src/syntax.c b/src/syntax.c
index d733f5b..d247e0d 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -7391,6 +7391,9 @@
     int		error = FALSE;
     int		color;
     int		is_normal_group = FALSE;	/* "Normal" group */
+#ifdef FEAT_TERMINAL
+    int		is_terminal_group = FALSE;	/* "Terminal" group */
+#endif
 #ifdef FEAT_GUI_X11
     int		is_menu_group = FALSE;		/* "Menu" group */
     int		is_scrollbar_group = FALSE;	/* "Scrollbar" group */
@@ -7616,6 +7619,10 @@
 
     if (STRCMP(HL_TABLE()[idx].sg_name_u, "NORMAL") == 0)
 	is_normal_group = TRUE;
+#ifdef FEAT_TERMINAL
+    else if (STRCMP(HL_TABLE()[idx].sg_name_u, "TERMINAL") == 0)
+	is_terminal_group = TRUE;
+#endif
 #ifdef FEAT_GUI_X11
     else if (STRCMP(HL_TABLE()[idx].sg_name_u, "MENU") == 0)
 	is_menu_group = TRUE;
@@ -8239,6 +8246,11 @@
 	    }
 #endif
 	}
+#ifdef FEAT_TERMINAL
+	else if (is_terminal_group)
+	    set_terminal_default_colors(
+		    HL_TABLE()[idx].sg_cterm_fg, HL_TABLE()[idx].sg_cterm_bg);
+#endif
 #ifdef FEAT_GUI_X11
 # ifdef FEAT_MENU
 	else if (is_menu_group)