abort when $version (if set) and $tag do not align

version is (only) set by the scala-release-2.11.x-dist build flow.

This is also a backstop for https://github.com/sbt/sbt-git/issues/35.

Ignore empty version (job is running outside of the flow).
Remove the default for build parameter SCALA_VER_SUFFIX

As the empty string is a a valid value.

I checked if this variable is used in other builds in the same way.
It is only used in this job:

    % ack SCALA_VER_SUFFIX
    job/scala-release-2.11.x
    30:# but, no default for SCALA_VER_SUFFIX, "" is a valid value for the final release.
    80:SCALA_VER="$SCALA_VER_BASE$SCALA_VER_SUFFIX"
    272:    -Dmaven.version.suffix=$SCALA_VER_SUFFIX\
    321:#     -Dmaven.version.suffix=$SCALA_VER_SUFFIX\
Merge pull request #96 from retronym/topic/scala-ver-suf

Remove the default for build parameter SCALA_VER_SUFFIX
Add new parameter to release job: SCALA_BINARY_VER

Otherwise, the build for privately published build of Scalacheck
fails for binary-compatible releases (ie, non-RCs) with:

    unresolved dependency: org.scala-lang.modules#scala-parser-combinators_2.11.0;1.0.1: not found
Merge pull request #97 from retronym/topic/scalacheck-scala-binary-version

Add new parameter to release job: SCALA_BINARY_VER
Pass 2.11, rather than 2.11.0, as scala.binary.version

To remedy the errors:

    Unable to resolve artifact: Missing:
    ----------
    1) org.scala-lang.modules:scala-partest_2.11.0:jar:1.0.0

in:

  https://scala-webapps.epfl.ch/jenkins/view/scala-release-2.11.x/job/scala-release-2.11.x/55
Merge pull request #98 from retronym/topic/scala-binary-version

Pass 2.11, rather than 2.11.0, as scala.binary.version
continuations-plugin cross suffixed by 2.11.0, rather than than 2.11

To remedy the error:

    Unable to resolve artifact: Missing:
    ----------
    1) org.scala-lang.plugins:scala-continuations-plugin_2.11:jar:1.0.1

In:

  https://scala-webapps.epfl.ch/jenkins/view/scala-release-2.11.x/job/scala-release-2.11.x/56/console
Merge pull request #99 from retronym/topic/continuations-cross

continuations-plugin cross suffixed by 2.11.0, rather than than 2.11
Merge pull request #100 from xeno-by/master

major cleanup of paradise builds
Merge pull request #101 from xeno-by/master

tsk tsk tsk, oh these final releases!
Merge pull request #102 from xeno-by/master

more cleanup for paradise builds
Merge pull request #95 from adriaanm/fullverprop

abort when $version (if set) and $tag do not align
Merge pull request #103 from xeno-by/master

fixes paradise builds after 2.11.0-SNAPSHOT has been evicted
Merge pull request #104 from xeno-by/master

an annoying typo that fixes the 2.11.x paradise build
Scala 2.12 awareness for Jenkins scripts
Merge pull request #105 from retronym/topic/2.12

Scala 2.12 awareness for Jenkins scripts
Temporarily disable IDE PR validation

Until https://github.com/scala-ide/uber-build/pull/46 and friends
are in place.
Merge pull request #106 from retronym/topic/2.12-ide-disable

Temporarily disable IDE PR validation
Revert "Temporarily disable IDE PR validation"

This reverts commit cf5cb7502d1708d238efadcb9cfecafe112cc76a.

I accidentally disabled partest integration, rather than IDE
validation.