Cocoa: Fix pre-window-creation event processing

Polling the event queue before NSApp had been allowed to finish
launching, in our case by starting our self-terminating run loop,
triggered an assertion inside NSApplication.

This fix, which makes all event processing functions capable of starting
it, makes that assertion less likely.

A more Cocoa-friendly fix would be to finish launching NSApp during
glfwInit and let people annoyed by the menu bar disabled it with
GLFW_COCOA_MENUBAR.  That may not be suitable for 3.3-stable, though.

Fixes #1543.

(cherry picked from commit 6e6805000a)

src/cocoa_init.m

@@ -447,9 +447,9 @@ static GLFWbool initializeTIS(void)
 
 - (void)applicationDidFinishLaunching:(NSNotification *)notification
 {
-    [NSApp stop:nil];
-
+    _glfw.ns.finishedLaunching = GLFW_TRUE;
     _glfwPlatformPostEmptyEvent();
+    [NSApp stop:nil];
 }
 
 - (void)applicationDidHide:(NSNotification *)notification

src/cocoa_window.m

@@ -891,10 +891,7 @@ int _glfwPlatformCreateWindow(_GLFWwindow* window,
     @autoreleasepool {
 
     if (!_glfw.ns.finishedLaunching)
-    {
         [NSApp run];
-        _glfw.ns.finishedLaunching = GLFW_TRUE;
-    }
 
     if (!createNativeWindow(window, wndconfig, fbconfig))
         return GLFW_FALSE;
@@ -1385,6 +1382,9 @@ void _glfwPlatformPollEvents(void)
 {
     @autoreleasepool {
 
+    if (!_glfw.ns.finishedLaunching)
+        [NSApp run];
+
     for (;;)
     {
         NSEvent* event = [NSApp nextEventMatchingMask:NSEventMaskAny
@@ -1404,6 +1404,9 @@ void _glfwPlatformWaitEvents(void)
 {
     @autoreleasepool {
 
+    if (!_glfw.ns.finishedLaunching)
+        [NSApp run];
+
     // I wanted to pass NO to dequeue:, and rely on PollEvents to
     // dequeue and send.  For reasons not at all clear to me, passing
     // NO to dequeue: causes this method never to return.
@@ -1422,6 +1425,9 @@ void _glfwPlatformWaitEventsTimeout(double timeout)
 {
     @autoreleasepool {
 
+    if (!_glfw.ns.finishedLaunching)
+        [NSApp run];
+
     NSDate* date = [NSDate dateWithTimeIntervalSinceNow:timeout];
     NSEvent* event = [NSApp nextEventMatchingMask:NSEventMaskAny
                                         untilDate:date
@@ -1439,6 +1445,9 @@ void _glfwPlatformPostEmptyEvent(void)
 {
     @autoreleasepool {
 
+    if (!_glfw.ns.finishedLaunching)
+        [NSApp run];
+
     NSEvent* event = [NSEvent otherEventWithType:NSEventTypeApplicationDefined
                                         location:NSMakePoint(0, 0)
                                    modifierFlags:0