patch 8.1.0970: text properties test fails when 'encoding' is not utf-8

Problem:    Text properties test fails when 'encoding' is not utf-8.
Solution:   Compare with original value of 'encoding'. (Christian Brabandt,
            closes #3986)
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 9108b8e..2a1b5ea 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -50,7 +50,9 @@
 set nocp viminfo+=nviminfo
 
 " Use utf-8 by default, instead of whatever the system default happens to be.
-" Individual tests can overrule this at the top of the file.
+" Individual tests can overrule this at the top of the file and use
+" g:orig_encoding if needed.
+let g:orig_encoding = &encoding
 set encoding=utf-8
 
 " REDIR_TEST_TO_NULL has a very permissive SwapExists autocommand which is for
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 311f30f..5ea5517 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -518,7 +518,8 @@
 
 " screenshot test with textprop highlighting
 funct Test_textprop_screenshots()
-  if !CanRunVimInTerminal() || &encoding != 'utf-8'
+  " The Vim running in the terminal needs to use utf-8.
+  if !CanRunVimInTerminal() || g:orig_encoding != 'utf-8'
     return
   endif
   call writefile([
diff --git a/src/version.c b/src/version.c
index cd45fa0..c4034ee 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    970,
+/**/
     969,
 /**/
     968,