patch 9.0.0869: bogus error when string used after :elseif

Problem:    Bogus error when string used after :elseif.
Solution:   Do not consider a double quote the start of a comment.
            (closes #11534)
diff --git a/src/ex_eval.c b/src/ex_eval.c
index e1c2889..68dc6d7 100644
--- a/src/ex_eval.c
+++ b/src/ex_eval.c
@@ -1173,7 +1173,8 @@
     {
 	// When skipping we ignore most errors, but a missing expression is
 	// wrong, perhaps it should have been "else".
-	if (skip && ends_excmd(*eap->arg))
+	// A double quote here is the start of a string, not a comment.
+	if (skip && *eap->arg != '"' && ends_excmd(*eap->arg))
 	    semsg(_(e_invalid_expression_str), eap->arg);
 	else
 	    result = eval_to_bool(eap->arg, &error, eap, skip, FALSE);
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index 4aa6bca..a23bac3 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -192,6 +192,16 @@
     call assert_equal('ab3j3b2c2b1f1h1km', g:Xpath)
 endfunc
 
+" Check double quote after skipped "elseif" does not give error E15
+func Test_skipped_elseif()
+  if "foo" ==? "foo"
+      let result = "first"
+  elseif "foo" ==? "foo"
+      let result = "second"
+  endif
+  call assert_equal('first', result)
+endfunc
+
 "-------------------------------------------------------------------------------
 " Test 4:   :return							    {{{1
 "-------------------------------------------------------------------------------
diff --git a/src/version.c b/src/version.c
index b16f860..10aa6de 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    869,
+/**/
     868,
 /**/
     867,