[cmake,release] Corrects setting of HAVE_* variables.

For generating the config.h file we use the HAVE_* variables instead
of the CMake ones *_FOUND, Unfortunately, we sometines to not set
HAVE_* to the value of the *_FOUND vriable but to its name. Usually
we only query whether these variable are set at all. While
this often (except for psurface) does not pose a problem, it is semantically
wrong. Therfore this patch fixes this.

Kudos to Ansgar for pointing to this problem.

cmake/modules/DuneMPI.cmake

@@ -21,7 +21,7 @@ find_package(MPI)
 find_package(Threads)
 
 if(MPI_CXX_FOUND)
-  set(HAVE_MPI MPI_CXX_FOUND)
+  set(HAVE_MPI ${MPI_CXX_FOUND})
   # We do not support the CXX bindings of MPI
   set(MPI_DUNE_COMPILE_FLAGS ${MPI_C_COMPILE_FLAGS} CACHE STRING
     "Compile flags used by DUNE when compiling MPI programs")

cmake/modules/FindUMFPack.cmake

@@ -92,7 +92,7 @@ else(UMFPACK_FOUND)
 endif(UMFPACK_FOUND)
 
 #set HAVE_UMFPACK for config.h
-set(HAVE_UMFPACK UMFPACK_FOUND)
+set(HAVE_UMFPACK ${UMFPACK_FOUND})
 
 #add all umfpack related flags to ALL_PKG_FLAGS, this must happen regardless of a target using add_dune_umfpack_flags
 if(UMFPACK_FOUND)