Moved LXXFLAGS to end of linking phase in Makefile

BA wouldn't build on my Linux Mint 14 desktop with

- GCC 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1)
- GNU Make 3.8.1
- `libgl1-mesa-dev` version 9.0-0ubuntu1
- `libglu1-mesa-dev` version 9.0-0ubuntu1
- `freeglut3-dev` version 2.6.0-4ubuntu1
- Kernel 3.5.0-17-generic amd64

Moving the `-lGL` et al. directives to the end of the linking statement
in the Makefile fixed the problem.  Fixes #14.