provide the det() keyword

Update issue 20
now the keyword det() is available for the variational formulation language

git-svn-id: svn+ssh://forge.imag.fr/var/lib/gforge/chroot/scmrepos/svn/life/trunk/life/trunk@8888 18f2cc81-8059-4896-b63e-f2d89ec8fd72

feel/feelvf/vf.hpp

@@ -96,6 +96,7 @@ struct ExtractGm
 #include <feel/feelvf/geometricdata.hpp>
 #include <feel/feelvf/stdmathfunctors.hpp>
 #include <feel/feelvf/trace.hpp>
+#include <feel/feelvf/det.hpp>
 #include <feel/feelvf/symm.hpp>
 #include <feel/feelvf/products.hpp>
 #include <feel/feelvf/norm.hpp>