lib-master: Added anvil_client_query_abort()

Marked functions parameters that are allowed to be NULL. Some APIs were also changed. The non-obvious APIs where NULL parameter was changed to "" are master_service_init() and auth_master_user_list_init(). These checks can currently be enabled only on a patched clang: http://llvm.org/bugs/show_bug.cgi?id=6786

lib-master: Added missing anvil_client_is_connected()

anvil client: Added more features. --HG-- branch : HEAD

lib-master: Added anvil client code. --HG-- branch : HEAD