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/indexed_view.cpp

@@ -388,7 +388,7 @@ void check_indexed_view()
 
 }
 
-void test_indexed_view()
+EIGEN_DECLARE_TEST(indexed_view)
 {
 //   for(int i = 0; i < g_repeat; i++) {
     CALL_SUBTEST_1( check_indexed_view() );