Patch to add a 'src' directory.

I'm about to start working on the main creddit executable, to improve it's overall structure, add some features, etc. etc... The main project is going to end up growing out of being just a single file 'main.c' (main.c is already getting a bit big as it is at 700 lines). This patch adds a 'src' directory which will contain the code for the main program (Currently just main.c). The idea is it'll keep us from littering the root of the project with tons of .c and .h files for the main executable, which can get a bit ugly.