[C++] Fix field encoding length when an array to be consistent with J…

…ava implementation. Issue #595.

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java

@@ -1032,7 +1032,7 @@ private CharSequence generatePrimitiveFieldMetaData(
             indent + "        return %2$d;\n" +
             indent + "    }\n",
             propertyName,
-            token.encoding().primitiveType().size()));
+            token.encoding().primitiveType().size() * token.arrayLength()));
 
         return sb;
     }