Attempted fix of Macaulay2#2907 by ringmap.cpp change

Tried adding block to ringmap code to detect the weyl algebra and change
how ring maps are computed.
Changed the order of multiplication for weyl algebras.
This did not seem to alter the behavior in the reference issue.

M2/Macaulay2/e/ringmap.cpp

@@ -165,8 +165,27 @@ ring_elem RingMap::eval_term(const Ring *sourceK,  // source coeff ring
       result_monom = M->make_one();
       temp_monom = M->make_one();
     }
-
-  if (!R->is_commutative_ring() || R->cast_to_SchurRing())
+  if (R->is_weyl_algebra())
+    {
+      for (index_varpower i = vp; i.valid(); ++i)
+        {
+          int v = first_var + i.var();
+          int e = i.exponent();
+          ring_elem g;
+          if (e >= 0)
+            g = _elem[v].bigelem;
+          else
+            g = R->invert(_elem[v].bigelem);
+          for (int j = 0; j < e; j++)
+            {
+              assert(v < nvars);
+              ring_elem tmp = R->mult(result, g);
+              R->remove(result);
+              result = tmp;
+            }
+        }
+    }
+  else if (!R->is_commutative_ring() || R->cast_to_SchurRing())
     {
       // This is the only non-commutative case so far
       for (index_varpower i = vp; i.valid(); ++i)