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Now the resources are installed and a lookup is performed to find them from
either (respectively) an environment var, the user's datadir and the
compile-time datadir.
Also the server is responsible for sharing the xml data so that all clients
get the same thing, from him over network.
Also libovcc is responsible for the DTD files (since it's a sort of spec)
while the actual XML data belongs to the server.

This gives better consistency by having tile and pawn related signals
next to each other, as well as making the board more self-sufficient
with it getting signals for all changes on it.

Also drop the build-time support for vertical layout, it's useless,
less nice, adds complexity and needs different packing options.

Add an icon for the application, based on the tile 13 by Salomé.

We use libgthread, but we didn't explicitly link it.  This used to
work because other libraries we link also links libgthread, but such
indirect dependencies are rejected by modern linkers.

Automake warns us that building subdir object without the subdir-object
option will break in the future;  and putting objects in the right
directory is a good thing anyway.

Automake changes its warnings from versions to versions, and they
generally are actually harmless, but can prevent generation of the
build system files.  So, still display all warnings, but do not
treat them as errors.

Also, make newer Automake happy by calling AM_PROG_AR if available.

Somehow the vapi hack to use a directory prefix for header did not run
anymore, probably because of new vala version 0.17 testing.
Fixed by using the same principle as in libovcc.

This reverts commit c17cc0e1.

We finaly want it since time has gone and it's fine now (current version is 0.17).

This field scoring implementation seem to work (in spite of hacks)
but need more testing and optimisation.

This change doesn't affect Vala API but breaks ABI and C API.