Make buildable with Panda

This makes it possible to build with `panda-build`, test with `panda-test` and install with `panda-install`. Without Panda, it can be built with `perl6 configure.pl6` (which also runs make), and then `make test` can be used as usual.

Because the path so the .so is worked out at compile time with `is native(...)`, that had to be changed to use the `trait_mod:<is>` workaround.

This also creates a dependency on LibraryMake to build; https://github.com/retupmoca/P6-LibraryMake/ (or `panda install LibraryMake`).