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

unsupported/test/cxx11_runqueue.cpp

@@ -227,7 +227,7 @@ void test_stress_runqueue()
   VERIFY(total.load() == 0);
 }
 
-void test_cxx11_runqueue()
+EIGEN_DECLARE_TEST(cxx11_runqueue)
 {
   CALL_SUBTEST_1(test_basic_runqueue());
   CALL_SUBTEST_2(test_empty_runqueue());