Additions to quaternion library

      add Makefile
      add quat_to_axis and quat_to_axis_v functions
      add quat to rotation matrix functions
      add vec3_init function
      add vec3_add, vec3_add_self and vec3_add_c_self functions
      add vec3_sub, vec3_sub_self, and vec3_sub_c_self functions
      add vec3 multiplication functions vec3_mul, vec3_mul_self
      add vec3 dot and cross product functions
      add vec3_len2 function (returns square of magnitude of vector)
      add vec3_normalize function
      add vec3 rotations functions vec3_rot_axis, vec3_rot_axis_self
      add vec3 distance functions vec3_dist, vec3_dist_c
      add quat_from_u2v function to calc. quaternion to rotate between 2 vectors
      add quat_dot function
      add quaternion nlerp and slerp functions
      add functions to apply relative yaw pitch roll
      add quat_decompose_twist_swing and quat_decompose_swing_twist functions

-- steve