freetdm: add __USE_BSD to ftdm_os, needed by unistd.h for usleep() and string.h to define strcasecmp()

add -Werror even when the compiler is unknown. This is just a work-around to gcc not being detected
         ad GNU by our current standalone build (not bootstrapped through FreeSWITCH)

libs/freetdm/src/ftmod/ftmod_zt/ftmod_zt.c

@@ -31,7 +31,6 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-
 #include "private/ftdm_core.h"
 #include "ftmod_zt.h"
 

libs/freetdm/src/include/ftdm_os.h

@@ -39,9 +39,12 @@
 extern "C" {
 #endif
 
+#if defined(__linux__) && !defined(__USE_BSD)
+#define __USE_BSD
+#endif
+
 #include "ftdm_declare.h"
 #include "ftdm_threadmutex.h"
-
 #include <string.h>
 
 #ifndef __WINDOWS__

libs/freetdm/src/testsangomaboost.c

@@ -49,12 +49,6 @@
 #include <string.h>
 #include <errno.h>
 
-#if defined(__linux__) && !defined(__USE_BSD)
-#define __USE_BSD
-#endif
-#ifndef WIN32
-#include <unistd.h>
-#endif
 #include "freetdm.h"