vim-patch:8.1.0648: custom operators can't act upon forced motion

Problem:    Custom operators can't act upon a forced motion. (Christian
            Wellenbrock)
Solution:   Add the forced motion to the mode() result. (Christian Brabandt,
            closes vim/vim#3490)
5976f8ff00

closes #8667
closes #9476

Christian Wellenbrock:

> For (most) built in text objects it's possible to force operation on
> them to be linewise, for example by using `dVab` (`:h o_V`,
> `motion_force`). When using custom text objects (defined as mappings
> by plugins for example), this doesn't currently work.
>
> Example:
>
>     onoremap x viw
>
> Open a file with a few lines each containing some words. With the
> cursor on any word, try:
>
> 1. `dw` (builtin) deletes some characters
> 2. `dVw` (builtin) deletes linewise
> 3. `dx` (from mapping) deletes some characters
> 4. `dVx` (from mapping) deletes some characters, but should delete
>    linewise

ref: https://github.com/wellle/targets.vim/issues/214
ref: https://gitter.im/neovim/neovim?at=5b379ff7f1664406610e7483

src/nvim/state.c

@@ -113,7 +113,7 @@ int get_real_state(void)
 /// @returns[allocated] mode string
 char *get_mode(void)
 {
-  char *buf = xcalloc(3, sizeof(char));
+  char *buf = xcalloc(4, sizeof(char));
 
   if (VIsual_active) {
     if (VIsual_select) {
@@ -160,6 +160,8 @@ char *get_mode(void)
     buf[0] = 'n';
     if (finish_op) {
       buf[1] = 'o';
+      // to be able to detect force-linewise/blockwise/characterwise operations
+      buf[2] = (char)motion_force;
     }
   }