Support various FFI types

[aleksisch]

This page contains all FFI semantics.
https://luajit.org/ext_ffi_semantics.html
Right now ljopt supports only int64 we should support all other types as well.

[ligurio]

Right now ljopt supports only int64 we should support all other types as well.

...and add more regression tests as it was suggested by @Buristan in discussion ¹.

Footnotes

1. https://github.com/ligurio/ljopt/pull/45#discussion_r2953975096 ↩