build_os2emx.patch in issue 3868 - update OS/2 EMX makefile and config files

Part of source_os2emx.patch in issue 3868:
  Include/pystrcmp.h:  OS/2 has same C APIs as Windows
  Lib/test/test_io.py: OS/2 has same behaviour as Windows for this test

Reviewed by Amaury Forgeot d'Arc
diff --git a/PC/os2emx/pyconfig.h b/PC/os2emx/pyconfig.h
index 1039d3d..13910dc 100644
--- a/PC/os2emx/pyconfig.h
+++ b/PC/os2emx/pyconfig.h
@@ -264,6 +264,9 @@
 /* Define if you have the <conio.h> header file. */
 #undef HAVE_CONIO_H
 
+/* Define to 1 if you have the `copysign' function. */
+#define HAVE_COPYSIGN 1
+
 /* Define if you have the <direct.h> header file. */
 #undef HAVE_DIRECT_H