Get rid of EIGEN_TEST_FUNC, unit tests must now be declared with EIGEN_DECLARE_TEST(mytest) { /* code */ }.

This provide several advantages:
- more flexibility in designing unit tests
- unit tests can be glued to speed up compilation
- unit tests are compiled with same predefined macros, which is a requirement for zapcc

test/sparse_vector.cpp

@@ -145,7 +145,7 @@ template<typename Scalar,typename StorageIndex> void sparse_vector(int rows, int
 
 }
 
-void test_sparse_vector()
+EIGEN_DECLARE_TEST(sparse_vector)
 {
   for(int i = 0; i < g_repeat; i++) {
     int r = Eigen::internal::random<int>(1,500), c = Eigen::internal::random<int>(1,500);