patch 8.2.1267: MS-Windows: tests may fail due to $PROMPT value

Problem:    MS-Windows: tests may fail due to $PROMPT value.
Solution:   Set $PROMPT for testing. (Taro Muraoka, closes #6510)

src/testdir/runtest.vim

@@ -117,6 +117,11 @@ set shellslash
 
 let s:srcdir = expand('%:p:h:h')
 
+if has('win32')
+  " avoid prompt that is long or contains a line break
+  let $PROMPT = '$P$G'
+endif
+
 " Prepare for calling test_garbagecollect_now().
 let v:testing = 1
 

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1267,
 /**/
     1266,
 /**/