Fixed a tiny one-pixel bug in renderer

Also got render compiling for OSX

v0.5.9 - Cross Compilation

Small amount of actual library code change, from problems only encountered after compiling for MS-Windows...
After installing a Max-OSX Cross-compiler, I've now drastically modified the Makefile to make managing binary builds across all 3 OSes much easier.
Also, rather pleasingly the total size of all binaries produced comes to 1.0MB 😃