Removing warnings when building Cocoa in 64-bit

NSInteger is defined as the native integer width, so these changes
remove implicit conversions that were causing precision warnings.

src/cocoa_monitor.m

@@ -97,8 +97,8 @@ static GLboolean modeIsGood(CGDisplayModeRef mode)
 static GLFWvidmode vidmodeFromCGDisplayMode(CGDisplayModeRef mode)
 {
     GLFWvidmode result;
-    result.width = CGDisplayModeGetWidth(mode);
+    result.width = (int) CGDisplayModeGetWidth(mode);
-    result.height = CGDisplayModeGetHeight(mode);
+    result.height = (int) CGDisplayModeGetHeight(mode);
     result.refreshRate = (int) CGDisplayModeGetRefreshRate(mode);
 
     CFStringRef format = CGDisplayModeCopyPixelEncoding(mode);

src/cocoa_window.m

@@ -519,7 +519,7 @@ static int translateKey(unsigned int key)
 - (void)otherMouseDown:(NSEvent *)event
 {
     _glfwInputMouseClick(window,
-                         [event buttonNumber],
+                         (int) [event buttonNumber],
                          GLFW_PRESS,
                          translateFlags([event modifierFlags]));
 }
@@ -532,7 +532,7 @@ static int translateKey(unsigned int key)
 - (void)otherMouseUp:(NSEvent *)event
 {
     _glfwInputMouseClick(window,
-                         [event buttonNumber],
+                         (int) [event buttonNumber],
                          GLFW_RELEASE,
                          translateFlags([event modifierFlags]));
 }