patch 8.1.2333: with modifyOtherKeys CTRL-^ doesn't work

Problem:    With modifyOtherKeys CTRL-^ doesn't work.
Solution:   Handle the exception.

src/getchar.c

@@ -1768,13 +1768,20 @@ vgetc(void)
 	    {
 		// A modifier was not used for a mapping, apply it to ASCII
 		// keys.  Shift would already have been applied.
-		if ((mod_mask & MOD_MASK_CTRL)
-			&& ((c >= '`' && c <= 0x7f)
-			    || (c >= '@' && c <= '_')))
+		if (mod_mask & MOD_MASK_CTRL)
+		{
+		    if ((c >= '`' && c <= 0x7f) || (c >= '@' && c <= '_'))
 		    {
 			c &= 0x1f;
 			mod_mask &= ~MOD_MASK_CTRL;
 		    }
+		    else if (c == '6')
+		    {
+			// CTRL-6 is equivalent to CTRL-^
+			c = 0x1e;
+			mod_mask &= ~MOD_MASK_CTRL;
+		    }
+		}
 		if ((mod_mask & (MOD_MASK_META | MOD_MASK_ALT))
 			&& c >= 0 && c <= 127)
 		{

src/testdir/test_termcodes.vim

@@ -1192,6 +1192,14 @@ func RunTest_modifyOtherKeys(func)
   call feedkeys('a' .. a:func('X', 9) .. "\<Esc>", 'Lx!')
   call assert_equal("Ø", getline(1))
 
+  " Ctrl-6 is Ctrl-^
+  split aaa
+  edit bbb
+  call feedkeys(a:func('6', 5), 'Lx!')
+  call assert_equal("aaa", bufname())
+  bwipe aaa
+  bwipe bbb
+
   bwipe!
   set timeoutlen&
 endfunc

src/version.c

@@ -737,6 +737,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2333,
 /**/
     2332,
 /**/