patch 8.1.0803: session file has problem with single quote in file name

Problem:    Session file has problem with single quote in file name. (Jon
            Crowe)
Solution:   Use a double quoted string.  Add a test.
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index 00631f1..145c91c 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -426,5 +426,19 @@
   call delete('Xtest_mks.out')
 endfunc
 
+func Test_mksession_quote_in_filename()
+  let v:errmsg = ''
+  %bwipe!
+  split another
+  split x'y\"z
+  mksession! Xtest_mks_quoted.out
+  %bwipe!
+  source Xtest_mks_quoted.out
+  call assert_true(bufexists("x'y\"z"))
+
+  %bwipe!
+  call delete('Xtest_mks_quoted.out')
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab