run-program patch / better UIOP support

Hi again,

after Elias mentioned his work on UIOP I've produced a small patch that improves compatibility with regards to process spawning quite a bit, see attached (or from [1]). Missing is the option to pass in custom streams (which some other implementations support), as that's quite a bit more work with the `ProcessBuilder` interface and would require shuffling data back and forth in a separate thread perhaps.

For Windows compatibility (for `process-pid`) I'm a bit stumped how that'd work with standard Java, thus it's currently unsupported.

Best regards, Olof

[1]: https://github.com/Ferada/abcl/tree/run-more-programs