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/dynalloc.cpp

@@ -119,7 +119,7 @@ template<typename T> void check_custom_new_delete()
 #endif
 }
 
-void test_dynalloc()
+EIGEN_DECLARE_TEST(dynalloc)
 {
   // low level dynamic memory allocation
   CALL_SUBTEST(check_handmade_aligned_malloc());