[m-dev.] Source distribution file name

[Julien Fischer]

Hi,

Previously we had a bunch of tarballs corresponding to the source distribution,

    mercury-compiler-<VERSION>.tar.gz
    mercury-extras-<VERSION>.tar.gz
    mercury-tests-<VERSION>.tar.gz

As these have all now been rolled into a single tar ball, I propose
that we change
the name to

   mercury-srcdist-<VERSION>.tar.gz

Any objections?

Cheers,
Julien.