OPAL does not compile with AMR Solver and unit tests

Compiling OPAL with ENABLE_AMR_SOLVER=1 and DBUILD_OPAL_UNIT_TESTS=1 gives the following compile error:

/home/scratch/OPAL/src/tests/opal_src/Distribution/GaussTest.cpp: In member function ‘virtual void GaussTest_FullSigmaTest1_Test::TestBody()’:
<command-line>:0:6: error: expected unqualified-id before numeric constant
/home/scratch/OPAL/src/tests/opal_src/Distribution/GaussTest.cpp:74:15: note: in expansion of macro ‘OPAL’
     OpalData *OPAL = OpalData::getInstance();
               ^

This is because OPAL is defined as preprocessor macro within CMake (with value 1):

[ 93%] Building CXX object tests/CMakeFiles/opal_unit_tests.dir/opal_src/Distribution/GaussTest.cpp.o
g++   -DBL_FORT_USE_UNDERSCORE -DBL_Linux -DBL_NOLINEVALUES -DBL_PARALLEL_IO -DBL_SPACEDIM=3 -DBL_USE_DOUBLE -DBL_USE_MPI -DMG_USE_F90_SOLVERS -DMG_USE_FBOXLIB -DNDEBUG -DOPAL  .... tests/opal_src/Distribution/GaussTest.cpp

This is done in CMakeModules/CCSEOptions.cmake :

list(APPEND BL_DEFINES "OPAL")

I don't see a reason to add OPAL here since afaik it is not used anywhere as such.

That said it might good to adopt camelCase for the variable name.