pcb-rnd - C89

The code is written in C, namely C89 for most parts with a few exceptions written in C99. It's not yet decided whether the code will be C89 or C99 long term. If it'll be C89, the C99 parts will be rewritten. If it'll be C99, new code can use C99 features freely. Until the decision, keep new code C89. Especially watch out for these:

comment: always use /* */, never //
don't mix variable declaration with code - open a new {} block, which will also scope your new variables, or better yet, split up the function into smaller, static functions, the compiler will inline them anyway
try to avoid vararg macros, use vararg functions instead