Polished ungzip crc32 check

lib/zlib/inflate.js

@@ -1356,8 +1356,8 @@ function inflate(strm, flush) {
         while (bits < 32) {
           if (have === 0) { break inf_leave; }
           have--;
-          hold += input[next++] << bits;
-          hold >>>= 0;
+          // Use '|' insdead of '+' to make sure that result is signed
+          hold |= input[next++] << bits;
           bits += 8;
         }
         //===//
@@ -1371,7 +1371,8 @@ function inflate(strm, flush) {
 
         }
         _out = left;
-        if ((state.flags ? hold : ZSWAP32(hold) >>> 0) !== state.check >>> 0) {
+        // NB: crc32 stored as signed 32-bit int, ZSWAP32 returns signed too
+        if ((state.flags ? hold : ZSWAP32(hold)) !== state.check) {
           strm.msg = 'incorrect data check';
           state.mode = BAD;
           break;