MDEV-5272 MTR/mysqltest overlays for included files do not work on Windows

client/mysqltest.cc

@@ -3034,6 +3034,10 @@ void open_file(const char *name)
       5.try in basedir
     */
 
+#ifdef __WIN__
+    fix_win_paths(curname, sizeof(curname));
+#endif
+
     bool in_overlay= opt_overlay_dir &&
                      !strncmp(curname, opt_overlay_dir, overlay_dir_len);
     bool in_suiteir= opt_overlay_dir && !in_overlay &&

mysql-test/suite/mtr2/overlay.inc

+select 2;
+

mysql-test/suite/mtr2/single.result

 select 1;
 1
 1
+select 2;
+2
+2

mysql-test/suite/mtr2/single.test

@@ -5,4 +5,8 @@
 # three times - once for the parent suite, and once for each overlay.
 # even if the test files are not overlayed.
 #
+# overlay.inc is overridden in mtr2-myisam, and there is an rdiff file.
+#
 select 1;
+source overlay.inc;
+

storage/myisam/mysql-test/mtr2/overlay.inc

+select 3;
+

storage/myisam/mysql-test/mtr2/single.rdiff

+--- suite/mtr2/single.result	2013-11-10 03:58:37.000000000 +0400
++++ suite/mtr2/single.reject	2013-11-10 03:59:08.000000000 +0400
+@@ -1,6 +1,6 @@
+ select 1;
+ 1
+ 1
+-select 2;
+-2
+-2
++select 3;
++3
++3