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/triangular.cpp

@@ -220,7 +220,7 @@ void bug_159()
   EIGEN_UNUSED_VARIABLE(m)
 }
 
-void test_triangular()
+EIGEN_DECLARE_TEST(triangular)
 {
   int maxsize = (std::min)(EIGEN_TEST_MAX_SIZE,20);
   for(int i = 0; i < g_repeat ; i++)