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/product_trmv.cpp

@@ -70,7 +70,7 @@ template<typename MatrixType> void trmv(const MatrixType& m)
   // TODO check with sub-matrices
 }
 
-void test_product_trmv()
+EIGEN_DECLARE_TEST(product_trmv)
 {
   int s = 0;
   for(int i = 0; i < g_repeat ; i++) {