This was committed as a temporary workaround in 82150f5641
as release builds were failing (only debug builds worked).
This adds `stdio.h` to the header which is now split into a file that
contains more specialized functionality.
Also move function body inside BPY_python_backtrace,
removing PyC_StackPrint as we have PyC_StackSpit() for
similar functionality that can be called from a debugger.
