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/array_reverse.cpp

@@ -123,7 +123,7 @@ template<typename MatrixType> void reverse(const MatrixType& m)
   VERIFY_IS_APPROX(x, m1(r, cols - 1 - c));
 }
 
-void test_array_reverse()
+EIGEN_DECLARE_TEST(array_reverse)
 {
   for(int i = 0; i < g_repeat; i++) {
     CALL_SUBTEST_1( reverse(Matrix<float, 1, 1>()) );