Script: Account for reverseMap name inconsistencies

There are a few cases where the opcode name doesn't match the name exactly.
These are mostly related with data pushes, and the cases for `OP_0` and `OP_1NEGATE` were
not handled as data pushes as the buf.length was 0. This adds these exceptions to the
`_chunkToString` method on Script.

References:
- e54ebbf600/src/script/script.cpp (L13)
- e54ebbf600/src/core_write.cpp (L75)

lib/script/script.js

@@ -228,7 +228,21 @@ Script.prototype._chunkToString = function(chunk, type) {
   if (!chunk.buf) {
     // no data chunk
     if (typeof Opcode.reverseMap[opcodenum] !== 'undefined') {
+      if (asm) {
+        // A few cases where the opcode name differs from reverseMap
+        // aside from 1 to 16 data pushes.
+        if (opcodenum === 0) {
+          // OP_0 -> 0
+          str = str + ' 0';
+        } else if(opcodenum === 79) {
+          // OP_1NEGATE -> 1
+          str = str + ' -1';
+        } else {
+          str = str + ' ' + Opcode(opcodenum).toString();
+        }
+      } else {
         str = str + ' ' + Opcode(opcodenum).toString();
+      }
     } else {
       var numstr = opcodenum.toString(16);
       if (numstr.length % 2 !== 0) {
@@ -242,7 +256,7 @@ Script.prototype._chunkToString = function(chunk, type) {
     }
   } else {
     // data chunk
-    if (opcodenum === Opcode.OP_PUSHDATA1 ||
+    if (!asm && opcodenum === Opcode.OP_PUSHDATA1 ||
       opcodenum === Opcode.OP_PUSHDATA2 ||
       opcodenum === Opcode.OP_PUSHDATA4) {
       str = str + ' ' + Opcode(opcodenum).toString();