SI-4270 Rename implicits to avoid name clashes.

This will fail implicit search in the next commit.
SI-4270 Disqualify in scope implicits that are shadowed.

If an expression wouldn't type check explicitly, it shouldn't be
allowed implicitly.

Employs typedIdent, which already does this sort of thing rather well,
instead of continuing to reimplement it in Implicits.

Remove check for non-implicit synonym, which is subsumed by typing an Ident.

Workaround Scaladoc oddity, by using an attributed select when the context
is deficient.
Fix for reflection.  Review/Use by @adriaanm
Breaks.break should return Nothing, not Unit
Suppress non-local return unchecked warnings.

There doesn't seem to be any way to do that by adding
a synthetic annotation.
fixes a checkinit problem
Merge pull request #702 from jsuereth/sbt-reflecton-fix

Fix for reflection.  Review/Use by @adriaanm
Merge pull request #704 from jdanbrown/patch-1

Breaks.break should return Nothing, not Unit
Merge pull request #705 from paulp/topic/unchecked

Suppress non-local return unchecked warnings.
Clarifying deprecation messages for numeric conversions in Predef
Clarifying deprecation for implicit and explicit usage of the x2y's in Predef
A tribute to https://github.com/scala/scala/pull/414
Don't crash if cpsParam is not on the classpath.

When checking if a piece of code needs the continuations plugin, the cpsParam classes may not be on the class path. Assume it does not need it in that case.
Don't use the BrowsingLoader for Java sources. 

When the presentation compiler needs a SourceLoader, instead of immediately adding the file 
to the compilation round it uses a fast parser to create symbols for all top-level class definitions. 
The fast parser assumes Scala sources, which is not always the case.
Don't require symbols to be loaded in the parser.

The parser special-cases primitive types. For comparing the name, it relied on having the symbols 
for primitive types already loaded, which is not always the case. The presentation compiler 
may parse sources for, say, scala.Int, and therefore the symbol for Int may not be yet available.
Remove NPE when `compileLate` sees sources during initialization.

When a symbol needed in Definitions is loaded, it may be that the corresponding source is newer than
the classfile. That will send it to `compileLate`, but no phase is yet set. We simply add it to the 
compilation pipeline and continue gracefully.
Merge pull request #709 from scalamacros/topic/suppresswarnings

A tribute to https://github.com/scala/scala/pull/414
rework Future.dispatchFuture a bit to fix bugs / optimize

This fixes a bug where _taskStack could batch a task
into the wrong executor, as previously commented in the
code.

It now uses the _taskStack machinery for the Future.apply
dispatch in addition to callback dispatch, so we can batch
Future(body) as well.

Less significantly, it micro-optimizes by combining some
different closures and Runnable into a Task object, so
there aren't as many objects created when storing and
dispatching a callback. So it saves a bit of memory
and runtime perhaps.
Refactoring and temporary commit before finishing the fix.
Merge pull request #706 from scalamacros/topic/fixcheckinit

fixes a checkinit problem