Trim unnecessarily required config vars

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.

cmake/Modules/opm-polymer-prereqs.cmake

@@ -3,7 +3,6 @@
 
 # defines that must be present in config.h for our headers
 set (opm-polymer_CONFIG_VAR
-	HAVE_ERT
 	)
 
 # dependencies