Do not use O_RDWR on semaphores on FreeBSD

This is forbidden (returns EINVAL)

posix/JackPosixSemaphore.cpp

@@ -32,8 +32,10 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 #define JACK_SEM_PREFIX "/jack_sem"
+#define SEM_DEFAULT_O 0
 #else
 #define JACK_SEM_PREFIX "jack_sem"
+#define SEM_DEFAULT_O O_RDWR
 #endif
 
 namespace Jack
@@ -152,7 +154,7 @@ bool JackPosixSemaphore::Allocate(const char* name, const char* server_name, int
     BuildName(name, server_name, fName, sizeof(fName));
     jack_log("JackPosixSemaphore::Allocate name = %s val = %ld", fName, value);
 
-    if ((fSemaphore = sem_open(fName, O_CREAT | O_RDWR, 0777, value)) == (sem_t*)SEM_FAILED) {
+    if ((fSemaphore = sem_open(fName, O_CREAT | SEM_DEFAULT_O, 0777, value)) == (sem_t*)SEM_FAILED) {
         jack_error("Allocate: can't check in named semaphore name = %s err = %s", fName, strerror(errno));
         return false;
     } else {
@@ -180,7 +182,7 @@ bool JackPosixSemaphore::ConnectInput(const char* name, const char* server_name)
         return true;
     }
 
-    if ((fSemaphore = sem_open(fName, O_RDWR)) == (sem_t*)SEM_FAILED) {
+    if ((fSemaphore = sem_open(fName, SEM_DEFAULT_O)) == (sem_t*)SEM_FAILED) {
         jack_error("Connect: can't connect named semaphore name = %s err = %s", fName, strerror(errno));
         return false;
     } else if (fSemaphore) {