removed -lrosthread from libuvc's mac ldflags

libuvc/manifest.xml

@@ -10,7 +10,7 @@
   <url>http://ros.org/wiki/libuvc</url>
   <export>
     <cpp cflags="-I${prefix}/libuvc/include" lflags="-L${prefix}/libuvc/lib -Wl,-rpath,-L${prefix}/libuvc/lib"/>
-    <cpp os="osx" cflags="-I${prefix}/libuvc/include" lflags="-L${prefix}/libuvc/lib -Wl,-rpath,-L${prefix}/libuvc/lib -lrosthread -framework CoreServices"/>
+    <cpp os="osx" cflags="-I${prefix}/libuvc/include" lflags="-L${prefix}/libuvc/lib -Wl,-rpath,-L${prefix}/libuvc/lib -framework CoreServices"/>
   </export>
   <rosdep name="libusb-1.0"/>
 </package>