Bug#845113: scala: Upgrade to 2.12.x

[Emmanuel Bourg]

Control: retitle -1 scala: Upgrade to 2.12.x

Hi Zax,

The probably of Scala 2.12 being integrated into Stretch is near zero.
The Scala developers decided to dump the Ant build we relied on, Scala
is now exclusively built with SBT and we don't have this build tool in
Debian.

If you want to see Scala 2.12 in Debian I invite you to either
reconstruct an Ant build script for the new version (the RC releases
still had it, so it might be possible) or help the ongoing effort to
package SBT (see #639910 and the recent discussions on the debian-java
mailing list).

Emmanuel Bourg