Fixed memory leak in matrix4f_det.
Forgot to delete the submatrix
ftr 2: Camera coding has been improved
Last changes:
- added mouse and keyboard support. Now you can press any mouse button and
  rotate the camera.
- following movement features have been added: strafe, roll, pitch, yaw
Known issues:
- this should be checked in future that the camera represents all rotations correctly.
  It is hard to imagine for me what is going in 3D space.