0.9.5: minor compile fixes, op+=/op*= for glm::quat

hi, i intended to make those into three different pull request, however the web i/f doen't let me. 2a52f56 and 137b296 are simple compile fixes for the test cases on linux. e299af6 adds quat::op+=(quat) and quat::op*=(quat) and also implements op+(quat,quat) and op*(quat,quat) interms of their member counterpart; i usually do this for consistency. i also added some additional test code.