patch 8.1.0639: text properties test fails on MS-Windows

Problem:    text properties test fails on MS-Windows
Solution:   Set fileformat to "unix".

src/testdir/test_textprop.vim

@@ -230,6 +230,7 @@ func Test_prop_byteoff()
   call prop_type_add('comment', {'highlight': 'Directory'})
   new
   call setline(1, ['line1', 'line2', ''])
+  set ff=unix
   call assert_equal(13, line2byte(3))
   call prop_add(1, 1, {'end_col': 3, 'type': 'comment'})
   call assert_equal(13, line2byte(3))

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    639,
 /**/
     638,
 /**/