Add IsPushOnly(const_iterator pc)

Allows IsPushOnly() to be applied to just part of the script for
OP_RETURN outputs.

src/script/script.cpp

@@ -210,9 +210,8 @@ bool CScript::IsPayToScriptHash() const
             this->at(22) == OP_EQUAL);
 }
 
-bool CScript::IsPushOnly() const
+bool CScript::IsPushOnly(const_iterator pc) const
 {
-    const_iterator pc = begin();
     while (pc < end())
     {
         opcodetype opcode;
@@ -227,3 +226,8 @@ bool CScript::IsPushOnly() const
     }
     return true;
 }
+
+bool CScript::IsPushOnly() const
+{
+    return this->IsPushOnly(begin());
+}

src/script/script.h

@@ -589,6 +589,7 @@ public:
     bool IsPayToScriptHash() const;
 
     /** Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical). */
+    bool IsPushOnly(const_iterator pc) const;
     bool IsPushOnly() const;
 
     /**