InputService: ensure mIsButtonOneDown is always set (#48)

...regardless of exceptions being thrown by the gesture functions.

These would throw when the maximum gesture duration of 1 minute would be
reached.

Thanks to https://github.com/redburn82 for pointing this out!

Closes #38, closes #46

app/src/main/java/net/christianbeier/droidvnc_ng/InputService.java

@@ -119,8 +119,8 @@ public static void onPointerEvent(int buttonMask, int x, int y, long client) {
 
 			// down, was up
 			if ((buttonMask & (1 << 0)) != 0 && !instance.mIsButtonOneDown) {
-				instance.startGesture(x, y);
 				instance.mIsButtonOneDown = true;
+				instance.startGesture(x, y);
 			}
 
 			// down, was down
@@ -130,8 +130,8 @@ public static void onPointerEvent(int buttonMask, int x, int y, long client) {
 
 			// up, was down
 			if ((buttonMask & (1 << 0)) == 0 && instance.mIsButtonOneDown) {
-				instance.endGesture(x, y);
 				instance.mIsButtonOneDown = false;
+				instance.endGesture(x, y);
 			}