Internals: Rename Ast on non-node classes (#3262). No functional change.

This commit has the following replacements applied:

	s/\bAstUserInUseBase\b/VNUserInUseBase/g;
        s/\bAstAttrType\b/VAttrType/g;
        s/\bAstBasicDTypeKwd\b/VBasicDTypeKwd/g;
        s/\bAstDisplayType\b/VDisplayType/g;
        s/\bAstNDeleter\b/VNDeleter/g;
        s/\bAstNRelinker\b/VNRelinker/g;
        s/\bAstNVisitor\b/VNVisitor/g;
        s/\bAstPragmaType\b/VPragmaType/g;
        s/\bAstType\b/VNType/g;
        s/\bAstUser1InUse\b/VNUser1InUse/g;
        s/\bAstUser2InUse\b/VNUser2InUse/g;
        s/\bAstUser3InUse\b/VNUser3InUse/g;
        s/\bAstUser4InUse\b/VNUser4InUse/g;
        s/\bAstUser5InUse\b/VNUser5InUse/g;
        s/\bAstVarType\b/VVarType/g;

src/V3Begin.cpp

@@ -41,7 +41,7 @@ private:
     // NODE STATE
     // Entire netlist:
     // AstNodeFTask::user1      -> bool, 1=processed
-    const AstUser1InUse m_inuser1;
+    const VNUser1InUse m_inuser1;
     bool m_anyFuncInBegin = false;
 
 public:
@@ -56,7 +56,7 @@ public:
 
 //######################################################################
 
-class BeginVisitor final : public AstNVisitor {
+class BeginVisitor final : public VNVisitor {
 private:
     // STATE
     BeginState* const m_statep;  // Current global state
@@ -271,7 +271,7 @@ public:
 
 //######################################################################
 
-class BeginRelinkVisitor final : public AstNVisitor {
+class BeginRelinkVisitor final : public VNVisitor {
     // Replace tasks with new pointer
 private:
     // NODE STATE