Improved build process for BEDOPS suite

I fixed changes that the default Homebrew environment was making (e.g. -O3 to -Os is reverted back to -O3; removed unused links to libxml2 and OpenGL libraries; other fixes that match build with pre-packaged binaries for reproducibility). Formula builds correctly with Xcode 5/LLVM 3.3svn environment and binaries appear to pass test suites.