patch 9.0.0930: cannot debug the Kitty keyboard protocol with TermDebug

Problem:    Cannot debug the Kitty keyboard protocol with TermDebug.
Solution:   Add Kitty keyboard protocol support to the libvterm fork.
            Recognize the escape sequences that the protocol generates.  Add
            the 'keyprotocol' option to allow the user to specify for which
            terminal what protocol is to be used, instead of hard-coding this.
            Add recognizing the kitty keyboard protocol status.

src/vim.h

@@ -2257,6 +2257,14 @@ typedef enum {
     ESTACK_SCRIPT,
 } estack_arg_T;
 
+// Return value of match_keyprotocol()
+typedef enum {
+    KEYPROTOCOL_NONE,
+    KEYPROTOCOL_MOK2,
+    KEYPROTOCOL_KITTY,
+    KEYPROTOCOL_FAIL
+} keyprot_T;
+
 // Flags for assignment functions.
 #define ASSIGN_VAR	0     // ":var" (nothing special)
 #define ASSIGN_FINAL	0x01  // ":final"