patch 8.0.1108: cannot specify mappings for the terminal window

Problem:    Cannot specify mappings for the terminal window.
Solution:   Add the :tmap command and associated code.  (Jacob Askeland,
            closes #2073)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index c290328..3c51b3a 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -4209,6 +4209,7 @@
 	case CMD_cmap:	    case CMD_cnoremap:
 	case CMD_lmap:	    case CMD_lnoremap:
 	case CMD_smap:	    case CMD_snoremap:
+	case CMD_tmap:	    case CMD_tnoremap:
 	case CMD_xmap:	    case CMD_xnoremap:
 	    return set_context_in_map_cmd(xp, cmd, arg, forceit,
 						     FALSE, FALSE, ea.cmdidx);
@@ -4220,6 +4221,7 @@
 	case CMD_cunmap:
 	case CMD_lunmap:
 	case CMD_sunmap:
+	case CMD_tunmap:
 	case CMD_xunmap:
 	    return set_context_in_map_cmd(xp, cmd, arg, forceit,
 						      FALSE, TRUE, ea.cmdidx);
@@ -4231,6 +4233,7 @@
 	case CMD_cmapclear:
 	case CMD_lmapclear:
 	case CMD_smapclear:
+	case CMD_tmapclear:
 	case CMD_xmapclear:
 	    xp->xp_context = EXPAND_MAPCLEAR;
 	    xp->xp_pattern = arg;