generate-git-snapshot: replace distribution dashes in version
generate-git-snapshot: replace distribution dashes in version

Wikimedia uses more specific distributions reusing the upstream name and
suffixed with '-wikimedia'.  Whenever $distribution is set, it is
injected in the version string by version_information().

When generating the original tarball, git buildpackage is given a
version such as:

 NoEpochVer: 2.0.0-wikimedia1+0~20150413152850+jessie-wikimedia~1.gbpe39408

From Debian Policy `5.6.12 Version`:

    "package management system will break the version number apart at
    the last hyphen in the string to determine the upstream_version and
    debian_revision"

git buildpackage yields:

 Uptream version: 2.0.0-wikimedia1+0~20150413152850+jessie
 Debian revision: wikimedia~1.gbpe39408

Instead of an upstream version of '2.0.0'.

When concatenating the version and distribution, replace any dashes in
$distribution by underscores.

 NoEpochVer: 2.0.0-wikimedia1+0~20150413152850+jessie_wikimedia~1.gbpe39408
 Upstream version: 2.0.0
 Debian revision: wikimedia1+0~20150413152850+jessie_wikimedia~1.gbpe39408

webtrekk-kane/jenkins-debian-glue,webtrekk-kane/jenkins-debian-glue,jbfavre/jenkins-debian-glue,n054/jenkins-debian-glue,tonin/jenkins-debian-glue,mika/jenkins-debian-glue,cclausen/jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,n054/jenkins-debian-glue,jbfavre/jenkins-debian-glue,bmiklautz/jenkins-debian-glue,hetznerZA/jenkins-debian-glue,tonin/jenkins-debian-glue,mika/jenkins-debian-glue,bmiklautz/jenkins-debian-glue,hashar/jenkins-debian-glue,cclausen/jenkins-debian-glue,kartikm/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,kartikm/jenkins-debian-glue,hashar/jenkins-debian-glue,hetznerZA/jenkins-debian-glue