Sympy 1.9 support

• deepcopy support was broken due to https://github.com/sympy/sympy/pull/21260
• clean up some constructors
• fix detection of sympy development versions

fixes #35 (closed), fixes !237 (closed)

pystencils/astnodes.py

@@ -692,6 +692,9 @@ class ResolvedFieldAccess(sp.Indexed):
     def __getnewargs__(self):
         return self.base, self.indices[0], self.field, self.offsets, self.idx_coordinate_values
 
+    def __getnewargs_ex__(self):
+        return (self.base, self.indices[0], self.field, self.offsets, self.idx_coordinate_values), {}
+
 
 class TemporaryMemoryAllocation(Node):
     """Node for temporary memory buffer allocation.
@@ -837,6 +840,9 @@ class ConditionalFieldAccess(sp.Function):
     def __getnewargs__(self):
         return self.access, self.outofbounds_condition, self.outofbounds_value
 
+    def __getnewargs_ex__(self):
+        return (self.access, self.outofbounds_condition, self.outofbounds_value), {}
+
 
 class NontemporalFence(Node):
     def __init__(self):