patch 8.1.1638: running tests leaves some files behind

Problem:    Running tests leaves some files behind.
Solution:   Delete the files. (Ozaki Kiichi, closes #4617)
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index a08cef7..9199ba7 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1528,10 +1528,10 @@
   call assert_equal([''], getbufline(buf, 1, '$'))
 
   let curbuf = bufnr('')
-  call writefile(['some', 'text'], 'otherName')
-  let buf = bufadd('otherName')
+  call writefile(['some', 'text'], 'XotherName')
+  let buf = bufadd('XotherName')
   call assert_notequal(0, buf)
-  call assert_equal(1, bufexists('otherName'))
+  call assert_equal(1, bufexists('XotherName'))
   call assert_equal(0, getbufvar(buf, '&buflisted'))
   call assert_equal(0, bufloaded(buf))
   call bufload(buf)
@@ -1554,6 +1554,7 @@
   call assert_equal(0, bufexists(buf2))
 
   bwipe someName
-  bwipe otherName
+  bwipe XotherName
   call assert_equal(0, bufexists('someName'))
+  call delete('XotherName')
 endfunc
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 3983b57..00cc287 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -1708,6 +1708,7 @@
   let winid = popup_create(bufnr(''), {})
   redraw
   call popup_close(winid)
+  call delete('XsomeFile')
 endfunc
 
 func Test_popupwin_width()
diff --git a/src/version.c b/src/version.c
index b5aac1a..c835eee 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1638,
+/**/
     1637,
 /**/
     1636,