Add the scala-compiler back to pants.ini pins.
Add the scala-compiler back to pants.ini pins.

This broke the Fsq.io build, but went unfixed because it happened
at the same time as all the Scala 2.11 commits and I was waiting
for those changes to stabalize before digging into the breakage.

(sapling split of d3c82bc069a6c044395ac90552355b1ac8774020)
foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio,foursquare/fsqio