add lodepng.c to simplify build process for c

[jeffboody]

Would you consider including this change so that the lodepng.cpp file does not need to be renamed for C?

[lvandeve]

Hi, it's indeed a bit odd that it has to be like this, but keeping two files up to date is also not guaranteed to be perfect, so I'd prefer to leave it as-is, sorry for the small inconvenience

[jeffboody]

I think you are under the impression that I simply made a duplicate copy of the cpp file. But I actually just included it from the c file. There is nothing extra to keep up-to-date because the only implementation is in the cpp file.

Can you take another look at the patch?

[lvandeve]

Hmm, it's a way indeed... I'm considering it. But it's still odd, just like the current "rename to c" version. So I might as well keep the current odd solution. Not sure yet :)

[miniupnp]

Why not a symbolic link ?