Make CScriptNum() take nMaxNumSize as an argument

While the existing numeric opcodes are all limited to 4-byte bignum
arguments, new opcodes will need different limits.

src/script/script.h

@@ -195,7 +195,10 @@ public:
         m_value = n;
     }
 
-    explicit CScriptNum(const std::vector<unsigned char>& vch, bool fRequireMinimal)
+    static const size_t nDefaultMaxNumSize = 4;
+
+    explicit CScriptNum(const std::vector<unsigned char>& vch, bool fRequireMinimal,
+                        const size_t nMaxNumSize = nDefaultMaxNumSize)
     {
         if (vch.size() > nMaxNumSize) {
             throw scriptnum_error("script number overflow");
@@ -318,8 +321,6 @@ public:
         return result;
     }
 
-    static const size_t nMaxNumSize = 4;
-
 private:
     static int64_t set_vch(const std::vector<unsigned char>& vch)
     {

src/test/scriptnum_tests.cpp

@@ -145,7 +145,7 @@ static void RunCreate(const int64_t& num)
 {
     CheckCreateInt(num);
     CScriptNum scriptnum(num);
-    if (scriptnum.getvch().size() <= CScriptNum::nMaxNumSize)
+    if (scriptnum.getvch().size() <= CScriptNum::nDefaultMaxNumSize)
         CheckCreateVch(num);
     else
     {