Document and test OP_RESERVED weirdness

Seems it was forgotten about when IsPushOnly() and the unittests were
written. A particular oddity is that OP_RESERVED doesn't count towards
the >201 opcode limit unlike every other named opcode.

src/script.cpp

@@ -327,6 +327,8 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
                 return false;
             if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE)
                 return false;
+
+            // Note how OP_RESERVED does not count towards the opcode limit.
             if (opcode > OP_16 && ++nOpCount > 201)
                 return false;
 

src/script.h

@@ -543,6 +543,10 @@ public:
             opcodetype opcode;
             if (!GetOp(pc, opcode))
                 return false;
+            // Note that IsPushOnly() *does* consider OP_RESERVED to be a
+            // push-type opcode, however execution of OP_RESERVED fails, so
+            // it's not relevant to P2SH as the scriptSig would fail prior to
+            // the P2SH special validation code being executed.
             if (opcode > OP_16)
                 return false;
         }

src/test/data/script_invalid.json

@@ -251,6 +251,7 @@
 ["1","VER", "OP_VER is reserved"],
 ["1","VERIF", "OP_VERIF is reserved"],
 ["1","VERNOTIF", "OP_VERNOTIF is reserved"],
+["1","RESERVED", "OP_RESERVED is reserved"],
 ["1","RESERVED1", "OP_RESERVED1 is reserved"],
 ["1","RESERVED2", "OP_RESERVED2 is reserved"],
 ["1","0xba", "0xba == OP_NOP10 + 1"],

src/test/script_tests.cpp

@@ -32,8 +32,12 @@ ParseScript(string s)
 
     if (mapOpNames.size() == 0)
     {
-        for (int op = OP_NOP; op <= OP_NOP10; op++)
+        for (int op = 0; op <= OP_NOP10; op++)
         {
+            // Allow OP_RESERVED to get into mapOpNames
+            if (op < OP_NOP && op != OP_RESERVED)
+                continue;
+
             const char* name = GetOpName((opcodetype)op);
             if (strcmp(name, "OP_UNKNOWN") == 0)
                 continue;
@@ -72,7 +76,7 @@ ParseScript(string s)
         }
         else if (mapOpNames.count(w))
         {
-            // opcode, e.g. OP_ADD or OP_1:
+            // opcode, e.g. OP_ADD or ADD:
             result << mapOpNames[w];
         }
         else