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/rvalue_types.cpp

@@ -43,7 +43,7 @@ template <typename MatrixType>
 void rvalue_copyassign(const MatrixType&) {}
 #endif
 
-void test_rvalue_types()
+EIGEN_DECLARE_TEST(rvalue_types)
 {
   CALL_SUBTEST_1(rvalue_copyassign( MatrixXf::Random(50,50).eval() ));
   CALL_SUBTEST_1(rvalue_copyassign( ArrayXXf::Random(50,50).eval() ));