osx: fix annoying focus behaviour (#689)

OS X has a global menu bar and a per app dock icon. Therefore, all
GUI applications launched from a terminal will become focused - even
if they don’t show any windows. Thereby the terminal loses focus.

Since is it very annoying to re-focus the terminal after each proxmark
client launch, this change makes the client unfocusable during launch
and restores the regular behaviour when a window is created.

client/util_darwin.m

@@ -12,6 +12,7 @@
 
 #import <Foundation/NSString.h>
 #import <Foundation/NSProcessInfo.h>
+#import <AppKit/NSApplication.h>
 
 static id activity = nil;
 
@@ -38,3 +39,17 @@ void enableAppNap() {
 void disableAppNap(const char* reason) { }
 void enableAppNap() { }
 #endif
+
+//OS X Version 10.6 is defined in OS X 10.6 and later
+#if defined(MAC_OS_X_VERSION_10_6)
+void makeUnfocusable() {
+	[NSApp setActivationPolicy:NSApplicationActivationPolicyProhibited];
+}
+
+void makeFocusable() {
+	[NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
+}
+#else
+void makeUnfocusable() { }
+void makeFocusable() { }
+#endif