restored dependency of pack.done on quick.bin
run test.bc as part of tests on 2.10.x

also added test.bc-opt target as binary compatibility differs between (non)optimized builds...
remove unused ant targets: test.ant, test.classload, test.positions
Formatting. Introduce {asm,forkjoin,fjbg}-classes props.
Remove duplication in java builds of fjbg/asm/forkjoin
Preparation for faster PR validation

Added starr.number, so that `ant -propertyfile starr.number -Dlocker.skip=1`
works across branches.

Introduced target `test.core`, which skips `test.stability`, since that requires
`locker == quick`, whereas `locker == starr` with the above settings.
(It's interesting to see for which files it fails when that assumption is broken.)

Stability will still be tested on a nightly basis. It's rarely broken.
Let continuations library sources determine docs.lib's actuality
Run test.scaladoc before test.suite. Fail fast.
ant clean only zaps the quick stage
Clean up pack targets. Better dependency tracking.

Target pack.@{project} is considered up to date iff
classes emitted by quick.@{project} are.

TODO: encapsulate "classes emitted by quick.@{project}".
For now, they are duplicated as references
to `${build-@{stage}.dir}/classes/@{destproject}`
(in staged-scalac and *.build.path)
Merge pull request #2314 from adriaanm/build-fixes

further tweaks to the ant build