Auto merge of #541 - joshleeb:joshleeb-graphics-tap_post_event, r=jdm

Add binding for CGEventTapPostEvent

This change adds the binding for CGEventTapPostEvent and adds a wrapper function CGEvent::post_from_tap to call the core-graphics function.

core-graphics/src/event.rs

@@ -607,12 +607,16 @@ impl CGEvent {
         }
     }
 
-    pub fn location(&self) -> CGPoint {
+    pub fn post_from_tap(&self, tap_proxy: CGEventTapProxy) {
         unsafe {
-            CGEventGetLocation(self.as_ptr())
+            CGEventTapPostEvent(tap_proxy, self.as_ptr());
         }
     }
 
+    pub fn location(&self) -> CGPoint {
+        unsafe { CGEventGetLocation(self.as_ptr()) }
+    }
+
     #[cfg(feature = "elcapitan")]
     pub fn post_to_pid(&self, pid: libc::pid_t) {
         unsafe {
@@ -734,6 +738,8 @@ extern {
     /// taps.
     fn CGEventPost(tapLocation: CGEventTapLocation, event: ::sys::CGEventRef);
 
+    fn CGEventTapPostEvent(tapProxy: CGEventTapProxy, event: ::sys::CGEventRef);
+
     #[cfg(feature = "elcapitan")]
     /// Post an event to a specified process ID
     fn CGEventPostToPid(pid: libc::pid_t, event: ::sys::CGEventRef);