error: ‘ptrdiff_t’ does not name a type

When I was compiling htmlcxx under Ubuntu 11.10, a compile error occurs. It shows

In file included from ParserDom.h:5:0,
                 from ParserDom.cc:1:
tree.h:118:21: error: 'ptrdiff_t' does not name a type

The error is occurred because Ubuntu 11.10 is using GCC 4.6.3.
Here is the common issues with GCC4.6/G++4.6: https://wiki.edubuntu.org/GCC4.6

To fix the error in tree.h:118:21 for ptrdiff_t, just add “#include <cstddef>” to the header.