Use Correct library path in various project files.

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user: Michael Guravage <michael.guravage@cwi.nl>
branch 'default'
changed src/ChangeLog
changed src/VirtualLeaf.pro
changed src/build_models/ChangeLog
changed src/build_models/plugin_auxingrowth.pro
changed src/build_models/plugin_meinhardt.pro
changed src/build_models/plugin_test.pro
changed src/libplugin.pro