The modules declare which configuration variables they need to have
present in config.h, not only their own but also defined in projects
using them.
However, a lot of these variables are not actually used in the headers!
This changeset removes all HAVE_XXX variables which is not present in
any opm/*.h* file in these projects, and thus there is no need for the
client to specify.
Note that only the variables used by the module *itself* should be
listed; the build system will setup the complete list from the
prerequisites.