Use block comments because ansi mode forbits c++ style comments
Fix c89 incompatibilities.

Might look to strict, but at least the compiler in pedantic mode will
catch any thing that is dangerous.
Test c++,ansi and c99 modes, break on warnings
Add mingw test rule and fix code so it compiles.

It currently compiles but doesn't link.
Merge pull request #10 from cesanta/ansi

Make the code compile in ansi, c99 and c++ modes