Add configure script to check for dependencies and sane build environment

[mike10004]

Currently, if you try building on a system that is, for example, lacking the jpeg or png build dependencies, you will wind up with compiler errors when the compiler fails to resolve the includes. This is jarring in a way that messages like "you need to install X" from a configure script would not be.

This is only relevant when building from source manually, as debian/control ensures the dependencies are present when debuild is invoked.