Show retransmit count for FreeBSD too. This may not actually

be implemented by the OS yet - the struct member starting with
a double underscore indicates that it's not fully implemented.

src/tcp_info.c

@@ -55,9 +55,13 @@ has_tcpinfo_retransmits(void)
 {
 #if defined(linux)
     return 1;
+#else
+#if defined(__FreeBSD__) && __FreeBSD_version >= 600000
+    return 1;
 #else
     return 0;
 #endif
+#endif
 }
 
 /*************************************************************/
@@ -79,9 +83,13 @@ get_tcpinfo_retransmits(struct iperf_interval_results *irp)
 {
 #if defined(linux)
     return irp->tcpInfo.tcpi_retransmits;
+#else
+#if defined(__FreeBSD__) && __FreeBSD_version >= 600000
+    return irp->tcpInfo.__tcpi_retransmits;
 #else
     return -1;
 #endif
+#endif
 }
 
 /*************************************************************/