state in updater construction were using mi at construction time. Don't
know why some compiler do accept to create an object with an argument
not yet created. Anyway some compiler do not accept ....

Add meshinterfacexHM.h. It is an interface using Hierarchical mesh
concept devised by N.C., and already implemented by himself and by
myself in a non committed version of the xDoubleCut distributed library.
Here is another one for FM. Works nice. Tested in a application.
Doesn't cost anything else compares to meshinterfacexRegion. It is
rather normal as extra cost of switching from iso support mesh to
background mesh only apply in a limited sequence of the FM (the
 beginning in the tested application)

This interface provides also a begin/end(what) like a region (mandatory
by new xTLS TLSFastMarchingValGradMode function where xRegion argument
have been replaced by a meshinterfacexHM instance. To be committed later)