Small fixes.

I had unpackOpcode() slightly wrong, and I made the libcore opcode
numbers always be four hex digits.

Change-Id: I4f988b8794b4b6c48ef91698a8e567fa46b96dac
diff --git a/opcode-gen/opcode-gen.awk b/opcode-gen/opcode-gen.awk
index c201b73..0b14a3f 100644
--- a/opcode-gen/opcode-gen.awk
+++ b/opcode-gen/opcode-gen.awk
@@ -113,7 +113,7 @@
 
     for (i = 0; i <= MAX_OPCODE; i++) {
         if (isUnused(i) || isOptimized(i)) continue;
-        printf("    int OP_%-28s = 0x%02x;\n", constName[i], i);
+        printf("    int OP_%-28s = 0x%04x;\n", constName[i], i);
     }
 }
 
@@ -416,6 +416,7 @@
     if (idx <= 255) {
         return idx;
     } else {
+        idx -= 256;
         return (idx * 256) + 255;
     }
 }