[C++] Combine libarrow/libarrow_io/libarrow_ipc

[asfimport]

From initial thirdparty users, it seems likely that users will link to all of these (or at least libarrow/libarrow_io) or none of them. It may be simpler for thirdparties for these core libraries to be a single link target instead of multiple.

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

Related issues:

• Arrow 0.3 release (blocks)

_{Note: This issue was originally created as ARROW-795. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
@kou @xhochy do you have any concerns about this? I think this will make development a bit simpler

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Kouhei Sutou / @kou:
I have no concern because the change doesn't increase external dependencies of libarrow. I'll update c_glib for this change after this change is merged into master.

[asfimport]

Wes McKinney / @wesm:
PR: #516

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 516
#516