Use "DEV" as the version number on the master branch

configure.ac:
    As above.
Make the build system forward compatible with automake

configure.ac:
    automake will require this setting in order to support source files in
    subdirectories in the future.
Update to more recent versions of the Mercury standard library

mercury/protobuf_runtime.m:
    The argument order of sparse_bitset.insert has changed.  Update to
    conform with this change.

    Several standard library predicates named 'new' are now deprecated.  Use
    the 'init' versions of these predicates.