Added custom fake support for variadic functions
Added custom fake support for variadic functions

Custom fake support for variadic functions was limited. The variable
parameters were not passed to the custom fake.

Now a va_list is passed to the custom fake, so it is possible to access
all the arguments. For instance, a custom fake for fprintf() could call
the real fprintf() like this:

int fprintf_custom(FILE *stream, const char *format, va_list ap) {
  if (fprintf0_fake.return_val < 0) // should we fail?
    return fprintf0_fake.return_val;
  return vfprintf(stream, format, ap);
}

usr42/fff,usr42/fff,usr42/fff,usr42/fff