* fix issues with "long double" type (useful to enforce the use of x87 registers)

* extend the documentation on "extending Eigen"

test/basicstuff.cpp

@@ -111,5 +111,6 @@ void test_basicstuff()
     CALL_SUBTEST( basicStuff(MatrixXi(8, 12)) );
     CALL_SUBTEST( basicStuff(MatrixXcd(20, 20)) );
     CALL_SUBTEST( basicStuff(Matrix<float, 100, 100>()) );
+    CALL_SUBTEST( basicStuff(Matrix<long double,Dynamic,Dynamic>(10,10)) );
   }
 }