Move binpac code into the main Zeek repository

This is based on commit 48f75b5f6415fe9d597e3e991cec635b1bc400dc from
the binpac repository.

tools/binpac/src/pac_datadep.h

@@ -0,0 +1,68 @@
+#ifndef pac_datadep_h
+#define pac_datadep_h
+
+// To provide a way to traverse through the data dependency graph.
+// That is, to evaluate X, what must be evaluated.
+
+#include "pac_common.h"
+#include "pac_dbg.h"
+
+class DataDepVisitor;
+
+class DataDepElement {
+public:
+    enum DDE_Type {
+        ATTR,
+        CASEEXPR,
+        EXPR,
+        FIELD,
+        INPUT_BUFFER,
+        PARAM,
+        TYPE,
+    };
+
+    DataDepElement(DDE_Type type);
+    virtual ~DataDepElement() {}
+
+    // Returns whether to continue traversal
+    bool Traverse(DataDepVisitor* visitor);
+
+    // Returns whether to continue traversal
+    virtual bool DoTraverse(DataDepVisitor* visitor) = 0;
+
+    DDE_Type dde_type() const { return dde_type_; }
+    Expr* expr();
+    Type* type();
+
+protected:
+    DDE_Type dde_type_;
+    bool in_traversal;
+};
+
+class DataDepVisitor {
+public:
+    virtual ~DataDepVisitor() {}
+    // Returns whether to continue traversal
+    virtual bool PreProcess(DataDepElement* element) = 0;
+    virtual bool PostProcess(DataDepElement* element) = 0;
+};
+
+class RequiresAnalyzerContext : public DataDepVisitor {
+public:
+    RequiresAnalyzerContext() : requires_analyzer_context_(false) {}
+
+    // Returns whether to continue traversal
+    bool PreProcess(DataDepElement* element) override;
+    bool PostProcess(DataDepElement* element) override;
+
+    bool requires_analyzer_context() const { return requires_analyzer_context_; }
+
+    static bool compute(DataDepElement* element);
+
+protected:
+    void ProcessExpr(Expr* expr);
+
+    bool requires_analyzer_context_;
+};
+
+#endif // pac_datadep_h