Allow swig files to include each other

[efoxepstein]

This adds the swig_includes option to java_wrap_cc to allow swig files to include other swig files.

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This change is 

[SanjayVas]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @efoxepstein)

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java/defs.bzl line 133 at r1 (raw file):

        package,
        deps = [],
        swig_includes = [],

nit: this should be None.

We only use empty list when the macro needs to do something with the list. In the case of deps, it's because we concatenate it and another list.

Code quote:

 []

[stevenwarejones]

@SanjayVas - are you planning on taking this pr over?

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @efoxepstein)

[SanjayVas]

Yes.

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @efoxepstein)