patch 8.1.1759: no mode char for terminal mapping from maparg()

Problem:    No mode char for terminal mapping from maparg().
Solution:   Check for TERMINAL mode. (closes #4735)

src/getchar.c

@@ -4009,6 +4009,8 @@ map_mode_to_chars(int mode)
 	    ga_append(&mapmode, 'n');			/* :nmap */
 	if (mode & OP_PENDING)
 	    ga_append(&mapmode, 'o');			/* :omap */
+	if (mode & TERMINAL)
+	    ga_append(&mapmode, 't');			/* :tmap */
 	if ((mode & (VISUAL + SELECTMODE)) == VISUAL + SELECTMODE)
 	    ga_append(&mapmode, 'v');			/* :vmap */
 	else

src/testdir/test_maparg.vim

@@ -29,6 +29,12 @@ function Test_maparg()
         \ 'nowait': 1, 'expr': 0, 'sid': sid, 'lnum': lnum + 1, 'rhs': 'bar',
 	\ 'buffer': 1},
         \ maparg('foo', '', 0, 1))
+  let lnum = expand('<sflnum>')
+  tmap baz foo
+  call assert_equal({'silent': 0, 'noremap': 0, 'lhs': 'baz', 'mode': 't',
+        \ 'nowait': 0, 'expr': 0, 'sid': sid, 'lnum': lnum + 1, 'rhs': 'foo',
+	\ 'buffer': 0},
+        \ maparg('baz', 't', 0, 1))
 
   map abc x<char-114>x
   call assert_equal("xrx", maparg('abc'))

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1759,
 /**/
     1758,
 /**/