B"H view1090: do not use pthreads

It *seems* that pthreads are used in dump1090 for I/! sample reading
only. So view1090 need not use pthread_exit.

view1090.c

@@ -298,11 +298,7 @@ int main(int argc, char **argv) {
     if (fd != ANET_ERR) 
       {close(fd);}
 
-#ifndef _WIN32
-    pthread_exit(0);
-#else
     return (0);
-#endif
 }
 //
 //=========================================================================