opm-grid-config.cmake always warns about dune-istl version incompatibility in opm-simulators

[blattms]

When I run CMake I get these warnings:

-- Finding package opm-grid using config mode
CMake Warning at /home/mblatt/src/dune/opm/opm-grid/opm-parallel-dbg/opm-grid-config.cmake:283 (message):
  Incompatible value "2" of variable "DUNE_ISTL_VERSION_MAJOR"
Call Stack (most recent call first):
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:144 (find_package)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:211 (find_and_append_package_to)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmLibMain.cmake:112 (find_and_append_package_list_to)
  CMakeLists.txt:111 (include)


CMake Warning at /home/mblatt/src/dune/opm/opm-grid/opm-parallel-dbg/opm-grid-config.cmake:287 (message):
  Incompatible value "3" of variable "DUNE_ISTL_VERSION_MINOR"
Call Stack (most recent call first):
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:144 (find_package)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:211 (find_and_append_package_to)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmLibMain.cmake:112 (find_and_append_package_list_to)
  CMakeLists.txt:111 (include)


CMake Warning at /home/mblatt/src/dune/opm/opm-grid/opm-parallel-dbg/opm-grid-config.cmake:291 (message):
  Incompatible value "1" of variable "DUNE_ISTL_VERSION_REVISION"
Call Stack (most recent call first):
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:144 (find_package)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmFind.cmake:211 (find_and_append_package_to)
  /home/mblatt/src/dune/opm/opm-common/cmake/Modules/OpmLibMain.cmake:112 (find_and_append_package_list_to)
  CMakeLists.txt:111 (include)

These version are already set by the buildsystem when searching for the dune modules. The test warns if MINOR or REVISION are not "".