QtDBus: fix build on MSVC2008 Debug mode.

Normally, searching for a V in a container of T using std::lower_bound
only needs an operator<(T,V). But in MSVC2008 debug mode, STL algorithms
perform some extra checks, such as ensuring the range passed to
std::lower_bound is sorted. This adds a requirement for operator<(T,T)
and operator<(V,T).

QtDBus didn't compile on MSVC2008+Debug since 1e37d854 (Sept 2012!)
because it missed those operator overloads for some private types.

Task-number: QTBUG-33473
Change-Id: I18902d86e6c58349eb7ba3601dc383ad5431c460
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>