We must not assume that the size of a function's return value is at
most `sizeof(ffi_arg)`, but rather have to use the size which already
has been determined for the return type if it is larger than
`sizeof(ffi_arg)`.
To be able to have a regression test, we export the required test
function from the zend-test extension, and make sure that the test
can be run on different platforms regardless of whether zend-tests was
built statically or dynamically.
Christoph M. Becker
05f3cd23ed