fixes black flicker on rotating the device

fixes #838

instead of rendering ad libitum on the map thread, we are now driving rendering from the UI thread on iOS via the map.renderSync() function. There are still white bars during the rotation, but the general content of the view is kept visible.

- upgrades GLFW to 3.1
- removes swapped/needsSwap in favor of a more explicit scheme
- View#invalidate() now replaces View#swap() and is called whenever the View needs to trigger a rerender. GLFW and Android to this right away, while iOS goes back to the main thread and does the Map redrawing as part of the GLKView update
- sets all iOS deployment targets to 7.0
- disables SQLite3 version check, since the library version changed on iOS 8.2

android/java/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxgl/views/NativeMapView.java

@@ -93,26 +93,10 @@ class NativeMapView {
         nativeRun(mNativeMapViewPtr);
     }
 
-    public void rerender() {
-        nativeRerender(mNativeMapViewPtr);
-    }
-
     public void update() {
         nativeUpdate(mNativeMapViewPtr);
     }
 
-    public void terminate() {
-        nativeTerminate(mNativeMapViewPtr);
-    }
-
-    public boolean needsSwap() {
-        return nativeNeedsSwap(mNativeMapViewPtr);
-    }
-
-    public void swapped() {
-        nativeSwapped(mNativeMapViewPtr);
-    }
-
     public void resize(int width, int height, float ratio, int fbWidth,
             int fbHeight) {
         if (width < 0) {
@@ -440,16 +424,10 @@ class NativeMapView {
 
     private native void nativeRun(long nativeMapViewPtr);
 
-    private native void nativeRerender(long nativeMapViewPtr);
-
     private native void nativeUpdate(long nativeMapViewPtr);
 
     private native void nativeTerminate(long nativeMapViewPtr);
 
-    private native boolean nativeNeedsSwap(long nativeMapViewPtr);
-
-    private native void nativeSwapped(long nativeMapViewPtr);
-
     private native void nativeResize(long nativeMapViewPtr, int width,
             int height, float ratio, int fbWidth, int fbHeight);