Disable C++11 warning from clang.

Since this header is included everywhere, this warning was getting
fairly annoying.
Set m_tss_used used to something so valgrind will stop complaining, note that since m_elements is 0 this has no effect
Initialize m_userDataSize propperly (discovered by asan)
Remove crazy log_info debug messange from virtual pipe
Make virtual pipe segments accept a const reference type. (#46)
Merge branch 'virtual_cref_item_type'. Closes #46.
Enable support for the C++11 override keyword. (#54)

Adds cpp0xtest/override_keyword.cpp which is an example program using
the override keyword.

In CMakeLists.txt, override_keyword.cpp is attempted compiled, and on
success, TPIE_CPP_OVERRIDE_KEYWORD is defined.

In config.h.cmake, a #define macro is inserted to turn `override` into
the empty string when it is not supported by the compiler.
Use the override keyword throughout TPIE.
Treat errors as warnings when testing for c++11 features
Add return statement to override_keyword.cpp.

With -Werror a compiler could be tempted to give a warning about a
missing return statement in non-void function, but that is not the
warning we are testing for.
Merge branch 'override'. Closes #54.
Switch progress_indicator_subindicator to a std::string. Fixes #55.
Remove parallel.h note about item_type (no longer relevant).
Support vectors with custom allocators.
Introduce job state. (#56)

This way it is easier to reason about code using the TPIE job manager,
since the tpie::job will ensure that enqueue, operator() and done()
are called only at the right time.

This also allows a job to be reentered into the job queue if that is
wanted.
Add ut-job repeat unit test.
Add ut-parallel_sort large item test.
Merge branch 'job_state'. Fixes #56.
Introduce maintain_order_type enum. (#52)
Change documentation on the maintainOrder parameter.