Enable IPv6 on Windows by default, and fix two type casts for IPv6 operations.

This commit was SVN r21586.

contrib/platform/win32/CMakeModules/ompi_configure.cmake

@@ -341,7 +341,7 @@ ELSE(NOT OPAL_ENABLE_FT_THREAD)
 ENDIF(NOT OPAL_ENABLE_FT_THREAD)
 
 OPTION( OPAL_ENABLE_IPV6 
-  "Enable IPv6 support, but only if the underlying system supports it." OFF)
+  "Enable IPv6 support, but only if the underlying system supports it." ON)
 MARK_AS_ADVANCED(OPAL_ENABLE_IPV6)
 
 OPTION( OPAL_ENABLE_TRACE 

ompi/mca/btl/tcp/btl_tcp_component.c

@@ -664,7 +664,7 @@ static int mca_btl_tcp_component_create_listen(uint16_t af_family)
         if (AF_INET6 == af_family) {
             int flg = 0;
             if (setsockopt (sd, IPPROTO_IPV6, IPV6_V6ONLY,
-                            &flg, sizeof (flg)) < 0) {
+                            (char *) &flg, sizeof (flg)) < 0) {
                 opal_output(0,
                     "mca_btl_tcp_create_listen: unable to disable v4-mapped addresses\n");
             }

orte/mca/oob/tcp/oob_tcp.c

@@ -589,7 +589,7 @@ mca_oob_tcp_create_listen(int *target_sd, unsigned short *target_port, uint16_t
         if (AF_INET6 == af_family) {
             int flg = 0;
             if (setsockopt (*target_sd, IPPROTO_IPV6, IPV6_V6ONLY,
-                            &flg, sizeof (flg)) < 0) {
+                            (char *) &flg, sizeof (flg)) < 0) {
                 opal_output(0,
                             "mca_oob_tcp_create_listen: unable to disable v4-mapped addresses\n");
             }