SI-7938 - parallel collections should use default ExecutionContext

Parallel collections now use `scala.concurrent.ExecutionContext`
by default.

The `ExecutionContextTaskSupport` is optimized to use the
`ForkJoinPool` underlying the `ExecutionContext` if possible.
Otherwise, a fallback `TaskSupport` that creates a reduction tree and
execute an operation through `Future`s is used.
Don't use runtime reflection from the batch compiler.

Not only does this save a big chunk of time on startup by avoiding
classloading and symbol table population, but it also seems to
improve steady state performance of the compiler.

Theory: JIT can optimize more aggressively without the
SynchronizedXxx decorators and the like being in the classloader.
See "Class Heirarchy Analyis" in [1]

This commit does this by:

  - Avoiding use of FromString in pattern matcher, instead
    using an established mechanism to parse system properties.
  - Changes FromString back to use OptManifest. AFAICT, this
    is now only a dependency of scala.tools.cmd.gen.Codegen,
    so this is just a defensive measure.

The REPL still uses runtime reflection, so will pay a little
performance tax.

Benchmark:

    avg shortest 10 times 744ms  # before
    avg shortest 10 times 675ms  # after

[1] https://wikis.oracle.com/display/HotSpotInternals/PerformanceTechniques
Make future-spec tests not spawn threads in constructors.
The future-spec tests were spawning threads in object constructors which
meant they were on the ragged edge of entering deadlock from the static
initialization lock acquired during the static initialization blocks we
use to construct object reference fields. My work on restructuring
lambdas pushed it over the edge. This commit refactors the tests to use
class constructors rather than object constructors.
Add a skeletal Delambdafy phase.
This commit adds a do-nothing phase called "Delambdafy" that will
eventually be responsible for doing the final translation of lambdas
into classes.
from Issue #3098

from Issue #3098, some typos.
Merge pull request #3099 from yinxusen/patch-1

Fix typo in ParIterableLike
SI-7776 post-erasure signature clashes are now macro-aware

"double definition: macro this and method that have same type after erasure"
This error doesn't make sense when macros are involved, because macros
expand at compile-time, where we're not affected by erasure. Moreover,
macros produce no bytecode, which means that we're safe from VerifyErrors.
Merge pull request #3086 from axel22/topic/pc-execution-context

 - parallel collections should use default ExecutionContext
SI-7634 resurrect the REPL's :sh command

ProcessResult had a companion object in 2.10 that somehow disappeared in
2.11. It only called "new ProcessResult(...)", so the REPL might just as
well do that.
Adds a setting to delay delambdafication. If set then uncurry lifts
the body of a lambda into a local def. Tests are included to show the
different tree shapes.
Refactor Erasure for delambdafication.
This commit is purely a refactor. It pulls code needed to adapt a tree
of one type into a tree of another type (by casting, boxing, coercing,
etc) out of Erasure and into common locations that will be usable
from the Delambdafy phase.
Flesh out the Delambdafy phase.

This commit puts a real body on the Delambdafy phase.

 From a lambda, Delambdafy will create
 1) a static forwarder at the top level of the class that contained
      the lambda
 2) a new top level class that
      a) has fields and a constructor taking the captured environment
(including possbily the "this" reference)
      b) an apply method that calls the static forwarder
      c) if needed a bridge method for the apply method
 3) an instantiation of the newly created class which replaces the
   lambda

Trees.scala is modified to add two more convenient factories
for templates and classdefs.

A few basic tests are included to verify that it works as expected.
Further commits will have additional tests.
Make GenASM not eliminate loadmodule on static methods.
During development of delayed delambdafy there was a problem where
GenASM would eliminate a loadmodule for all methods defined within that
module even if those methods were static. The result would be broken
byte code that failed verification. This commit fixes that and adds a
test.
Make specialization aware of anonymous functions.
During development of late delmabdafying there was a problem where
specialization would undo some of the work done in uncurry if the body
of the lambda had a constant type. That would result in a compiler crash
as when the delambdafy phase got a tree shape it didn't understand.
This commit has a fix and a test.
Create test variants where delambdafication alters signatures.
This commit includes several tests where there's a variation in
signatures between inline delambdafication and method based
delambdafication.
Force several tests to run using inline delambdafication.
The differences when running with method based delambdafication aren't
important enough yet to create specialized versions that use method
based delambdafication.
Merge pull request #3095 from retronym/topic/opt-no-runtime-reflect

Don't use runtime reflection from the batch compiler.
Updated Eclipse .classpath of partest and scaladoc projects

The version of some of the dependencies used in partest and scaladoc projects
did not match the version defined in `version.properties`. This prevented the
above projects from compiling correctly because the old dependencies were not
available in the local maven repository.
Removed Eclipse .project and .classpath for `plugintemplate` project

According to @gkossakowski this project doesn't need to be imported (and,
furtheremore, importing it in the current form results in errors in Eclipse),
hence I'm removing it.
Updated instructions for setting up Eclipse for Scala development