Missing Headers

When trying to compile the UDF example project on a pristine CDH4 system with
Ubuntu 12.04 and the impalae-dev-tools installed, it is not possible to
compile due to missing headers for C-style string manipulations.

This commit adds the headers and replaces the C header with the correct C++
reference.
Merge pull request #4 from grundprinzip/feature/ubuntu_udf_setup

Missing headers