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/householder.cpp

@@ -133,7 +133,7 @@ template<typename MatrixType> void householder(const MatrixType& m)
   VERIFY_IS_APPROX(m3 * m5, m1); // test evaluating rhseq to a dense matrix, then applying
 }
 
-void test_householder()
+EIGEN_DECLARE_TEST(householder)
 {
   for(int i = 0; i < g_repeat; i++) {
     CALL_SUBTEST_1( householder(Matrix<double,2,2>()) );