patch 8.2.1314: Vim9: rule for comment after :function is confusing

Problem:    Vim9: rule for comment after :function is confusing.
Solution:   Allow double quoted comment after :function in vim9script.
            (closes #6556)

src/testdir/test_vim9_script.vim

@@ -2284,6 +2284,10 @@ def Test_vim9_comment()
       'vim9script',
       'function # comment',
       ])
+  CheckScriptFailure([
+      'vim9script',
+      'function " comment',
+      ], 'E129:')
   CheckScriptFailure([
       'vim9script',
       'function# comment',
@@ -2333,11 +2337,11 @@ def Test_vim9_comment()
       'func Test() " comment',
       'endfunc',
       ])
-  CheckScriptFailure([
+  CheckScriptSuccess([
       'vim9script',
       'func Test() " comment',
       'endfunc',
-      ], 'E488:')
+      ])
 
   CheckScriptSuccess([
       'def Test() # comment',

src/userfunc.c

@@ -2832,7 +2832,8 @@ def_function(exarg_T *eap, char_u *name_arg)
     if (*p == '\n')
 	line_arg = p + 1;
     else if (*p != NUL
-	    && !(*p == '"' && !(vim9script || eap->cmdidx == CMD_def))
+	    && !(*p == '"' && (!vim9script || eap->cmdidx == CMD_function)
+						     && eap->cmdidx != CMD_def)
 	    && !(*p == '#' && (vim9script || eap->cmdidx == CMD_def))
 	    && !eap->skip
 	    && !did_emsg)

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1314,
 /**/
     1313,
 /**/