Declare a need to know if UMFPACK is available

Note that the variable HAVE_UMFPACK is not set by FindSuiteSparse,
but by OpmAliases.

cmake/Modules/Finddune-istl.cmake

@@ -49,6 +49,7 @@ int main (void) {
   HAVE_MPI;
   HAVE_PARMETIS;
   HAVE_SUPERLU;
+  HAVE_UMFPACK;
   SUPERLU_MIN_VERSION_4_3;
   SUPERLU_POST_2005_VERSION
   ")

cmake/Modules/OpmAliases.cmake

@@ -8,6 +8,7 @@ function (set_aliases)
   # hardcoded list of "dune-var opm-var" pairs, where the components
   # are separated by space
   set (aliases
+	"HAVE_UMFPACK             HAVE_SUITESPARSE_UMFPACK_H"
 	)
   foreach (alias IN LISTS aliases)
 	# convert entry "X Y" into a list "X;Y", then pick apart