some advancements for Richards equation

Common/Context.cpp

@@ -87,7 +87,7 @@ CTX::CTX()
     color.mesh.carousel[i] = 0;
 }
 
-CTX *CTX::_instance = 0;
+CTX *CTX::_instance = NULL;
 
 CTX *CTX::instance()
 {

Geo/MLine.cpp

@@ -58,5 +58,5 @@ void MLine::getIntegrationPoints(int pOrder, int *npts, IntPt **pts)
 
 double MLine::getInnerRadius()
 {
-  return _v[0]->distance(_v[1]);
+  return _v[0]->distance(_v[1]) * .5;
 }