add Bullet 2.x constraint solver tests for hinge, with large mass ratio

experiment with Midi controls in PairBenchmark to tune variables (will move it into a utility class, so every demo can easier use it in the future)
fix issue with broadphase, not initializing all pairs properly at pair array overflow

btgui/MidiTest/cmidiin.cpp

@@ -58,7 +58,7 @@ int main( int argc, char *argv[] )
     std::cout << "\nReading MIDI input ... press <enter> to quit.\n";
     char input;
     std::cin.get(input);
-	getchar();
+//	getchar();
 
 
  cleanup: