Compiler warnings from version.cpp

[feedhandler]

Just a minor issue: a couple of compiler warnings are generated env.CreateVersion():

build/src/gcc62/dbg/x86_64/c++1z/working/src/version.cpp: In function 'build::identity::dependencies_t build::initialise_dependencies()':

= Warning 1 =
_build/src/gcc62/dbg/x86_64/c++1z/working/src/version.cpp:65:38: warning: typedef 'dependency_t' locally defined but not used [-Wunused-local-typedefs]

 typedef identity::dependency_t   dependency_t;
                                  ^~~~~~~~~~~~

= Warning 2 =
_build/src/gcc62/dbg/x86_64/c++1z/working/src/version.cpp:66:38: warning: typedef 'revisions_t' locally defined but not used [-Wunused-local-typedefs]

 typedef identity::revisions_t    revisions_t;
                                  ^~~~~~~~~~~