keymap, terminal: more keycodes #9810

- input: recognize <kEqual>, <kComma>
- terminal.c: If we need to support function key, a change must be made
  in libvtermkey. Currently, it emulates strictly VT220 terminal, and
  returning numeric value in 'normal' mode is the expected behaviour.

closes #9810

src/nvim/getchar.c

@@ -1431,6 +1431,8 @@ int vgetc(void)
         case K_KMULTIPLY:   c = '*'; break;
         case K_KENTER:      c = CAR; break;
         case K_KPOINT:      c = '.'; break;
+        case K_KCOMMA:      c = ','; break;
+        case K_KEQUAL:      c = '='; break;
         case K_K0:          c = '0'; break;
         case K_K1:          c = '1'; break;
         case K_K2:          c = '2'; break;