patch 8.0.0258: mksession test leaves file behind

Problem:    mksession test leaves file behind.
Solution:   Delete the file.  Rename files to start with "X".
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index 77025c8..a51180c 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -22,7 +22,7 @@
     \   'aä Ä  two multiByte characters',
     \   'Aäöü  three mulTibyte characters'
     \ ])
-  let tmpfile = tempname()
+  let tmpfile = 'Xtemp'
   exec 'w! ' . tmpfile
   /^start:
   set wrap
@@ -63,8 +63,8 @@
   norm! j016|3zl
   split
   call wincol()
-  mksession! test_mks.out
-  let li = filter(readfile('test_mks.out'), 'v:val =~# "\\(^ *normal! 0\\|^ *exe ''normal!\\)"')
+  mksession! Xtest_mks.out
+  let li = filter(readfile('Xtest_mks.out'), 'v:val =~# "\\(^ *normal! 0\\|^ *exe ''normal!\\)"')
   let expected = [
     \   'normal! 016|',
     \   'normal! 016|',
@@ -96,7 +96,7 @@
   call assert_equal(expected, li)
   tabclose!
 
-  call delete('test_mks.out')
+  call delete('Xtest_mks.out')
   call delete(tmpfile)
   let &wrap = wrap_save
 endfunc
@@ -104,10 +104,10 @@
 func Test_mksession_winheight()
   new
   set winheight=10 winminheight=2
-  mksession! test_mks.out
-  source test_mks.out
+  mksession! Xtest_mks.out
+  source Xtest_mks.out
 
-  " call delete('test_mks.out')
+  call delete('Xtest_mks.out')
 endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index d3dc088..aaeb258 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    258,
+/**/
     257,
 /**/
     256,