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/qr_fullpivoting.cpp

@@ -125,7 +125,7 @@ template<typename MatrixType> void qr_verify_assert()
   VERIFY_RAISES_ASSERT(qr.logAbsDeterminant())
 }
 
-void test_qr_fullpivoting()
+EIGEN_DECLARE_TEST(qr_fullpivoting)
 {
   for(int i = 0; i < 1; i++) {
     CALL_SUBTEST_5( qr<Matrix3f>() );