patch 8.2.0588: Putty does not use "sgr" 'ttymouse' by default

Problem:    Putty does not use "sgr" 'ttymouse' by default.
Solution:   Make "sgr" the default for Putty. (Christian Brabandt,
            closes #5942)
diff --git a/src/version.c b/src/version.c
index f95b2a5..6b57804 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    588,
+/**/
     587,
 /**/
     586,