Fix #2186: Synchronize classpath handling with Scala 2.12

This commit is a very crude port of the classpath handling as it exists
in the 2.12.x branch of scalac (hash: 232d95a198c94da0c6c8393624e83e9b9ac84e81),
this replaces the existing Classpath code that was adapted from scalac
years ago.

This code was written by Grzegorz Kossakowski, Michał Pociecha, Lukas
Rytz, Jason Zaugg and other scalac contributors, many thanks to them!

For more information on this implementation, see the description of the
PR that originally added it to scalac: https://github.com/scala/scala/pull/4060

Changes made to the copied code to get it to compile with dotty:
- Rename scala.tools.nsc.util.ClassPath to dotty.tools.io.ClassPath
- Rename scala.tools.nsc.classpath.* to dotty.tools.dotc.classpath.*
- Replace "private[nsc]" by "private[dotty]"
- Changed `isClass` methods in FileUtils to skip Scala 2.11
  implementation classes (needed until we stop being retro-compatible with
  Scala 2.11)

I also copied PlainFile.scala from scalac to get access to
`PlainNioFile`.

1 files changed, 14 insertions, 9 deletions

diff --git a/AUTHORS.md b/AUTHORS.md
index db2f34a56..e197a6c5c 100644
--- a/AUTHORS.md
+++ b/AUTHORS.md
@@ -1,23 +1,28 @@
-The dotty compiler frontend has been developed since November 2012 by Martin Odersky. It is expected and hoped for 
+The dotty compiler frontend has been developed since November 2012 by Martin Odersky. It is expected and hoped for
 that the list of contributors to the codebase will grow quickly. Dotty draws inspiration and code from the original
-Scala compiler "nsc", which is developed at [scala/scala](https://github.com/scala/scala). 
+Scala compiler "nsc", which is developed at [scala/scala](https://github.com/scala/scala).
 
 The majority of the dotty codebase is new code, with the exception of the components mentioned below. We have for each component tried to come up with a list of the original authors in the  [scala/scala](https://github.com/scala/scala) codebase. Apologies if some major authors were omitted by oversight.
 
 `dotty.tools.dotc.ast`
 
-> The syntax tree handling is mostly new, but some elements, such as the idea of tree copiers and the `TreeInfo` module, 
-> were adopted from  [scala/scala](https://github.com/scala/scala). 
+> The syntax tree handling is mostly new, but some elements, such as the idea of tree copiers and the `TreeInfo` module,
+> were adopted from  [scala/scala](https://github.com/scala/scala).
 > The original authors of these parts include Martin Odersky, Paul Phillips, Adriaan Moors, and Matthias Zenger.
 
+`dotty.tools.dotc.classpath`
+
+> The classpath handling is taken mostly as is from [scala/scala](https://github.com/scala/scala).
+> The original authors were Grzegorz Kossakowski, Michał Pociecha, Lukas  Rytz, Jason Zaugg and others.
+
 `dotty.tools.dotc.config`
 
-> The configuration components were adapted and extended from  [scala/scala](https://github.com/scala/scala). 
+> The configuration components were adapted and extended from  [scala/scala](https://github.com/scala/scala).
 > The original sources were authored by Paul Phillips with contributions from Martin Odersky, Miguel Garcia and others.
-  
+
 `dotty.tools.dotc.core`
 
-> The core data structures and operations are mostly new. Some parts (e.g. those dealing with names) were adapted from  [scala/scala](https://github.com/scala/scala). 
+> The core data structures and operations are mostly new. Some parts (e.g. those dealing with names) were adapted from  [scala/scala](https://github.com/scala/scala).
 > These were originally authored by Martin Odersky, Adriaan Moors, Jason Zaugg, Paul Phillips, Eugene Burmako and others.
 
 `dotty.tools.dotc.core.pickling`
@@ -41,7 +46,7 @@ The majority of the dotty codebase is new code, with the exception of the compon
 
 > The utilities package is a mix of new and adapted components. The files in  [scala/scala](https://github.com/scala/scala) were originally authored by many people,
 > including Paul Phillips, Martin Odersky, Sean McDirmid, and others.
-  
+
 `dotty.tools.io`
 
 > The I/O support library was adapted from current Scala compiler. Original authors were Paul Phillips and others.
@@ -53,7 +58,7 @@ The majority of the dotty codebase is new code, with the exception of the compon
 > the needs of dotty. Original authors include: Adrian Moors, Lukas Rytz,
 > Grzegorz Kossakowski, Paul Phillips
 
-`dotty.tools.dotc.sbt and everything in bridge/`
+`dotty.tools.dotc.sbt and everything in sbt-bridge/`
 
 > The sbt compiler phases are based on
 > https://github.com/adriaanm/scala/tree/sbt-api-consolidate/src/compiler/scala/tools/sbt