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)
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 60805f1..3cf2a50 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -117,6 +117,11 @@
 
 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
 
diff --git a/src/version.c b/src/version.c
index 3847ec9..e4e7024 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1267,
+/**/
     1266,
 /**/
     1265,