SI-6362 & SI-5924 removes caches in the macro API

As recent experience shows, it's hardly possible to provide a global cache
that persists between compilation runs: http://groups.google.com/group/scala-ide-user/browse_thread/thread/b1cab5588ff21f7f.
Therefore I think we need to remove Context.globalCache.

Speaking of a per-run cache, it looks like Context.cache can be
to a certain extent emulated with attachments. Otherwise, one could write
a JVM-wide static cache weakly indexed by compilation run instances
(that are available via c.currentRun).

For now I think we need to remove both caches. If macro writers really need
that functionality, we could come up with a well-thought API later.

src/compiler/scala/reflect/macros/runtime/Infrastructure.scala

@@ -33,8 +33,4 @@ trait Infrastructure {
   }
 
   val currentMacro: Symbol = expandee.symbol
-
-  val globalCache: scala.collection.mutable.Map[Any, Any] = universe.analyzer.globalMacroCache
-
-  val cache: scala.collection.mutable.Map[Any, Any] = universe.analyzer.perRunMacroCache.getOrElseUpdate(currentMacro, collection.mutable.Map[Any, Any]())
 }

src/compiler/scala/tools/nsc/typechecker/Macros.scala

@@ -49,9 +49,6 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
   import MacrosStats._
   def globalSettings = global.settings
 
-  val globalMacroCache = collection.mutable.Map[Any, Any]()
-  val perRunMacroCache = perRunCaches.newMap[Symbol, collection.mutable.Map[Any, Any]]
-
   /** `MacroImplBinding` and its companion module are responsible for
    *  serialization/deserialization of macro def -> impl bindings.
    *

src/reflect/scala/reflect/macros/Infrastructure.scala

@@ -77,23 +77,4 @@ trait Infrastructure {
   /** Returns a macro definition which triggered this macro expansion.
    */
   val currentMacro: Symbol
-
-  // todo. redo caches as discussed on Reflecting Meeting 2012/03/29
-  // https://docs.google.com/document/d/1oUZGQpdt2qwioTlJcSt8ZFQwVLTvpxn8xa67P8OGVpU/edit
-
-  /** A cache shared by all invocations of all macros across all compilation runs.
-   *
-   *  Needs to be used with extreme care, since memory leaks here will swiftly crash the presentation compiler.
-   *  For example, Scala IDE typically launches a compiler run on every edit action so there might be hundreds of runs per minute.
-   */
-  val globalCache: scala.collection.mutable.Map[Any, Any]
-
-  /** A cache shared by all invocations of the same macro within a single compilation run.
-   *
-   *  This cache is cleared automatically after a compilation run is completed or abandoned.
-   *  It is also specific to a particular macro definition.
-   *
-   *  To share data between different macros and/or different compilation runs, use ``globalCache''.
-   */
-  val cache: scala.collection.mutable.Map[Any, Any]
 }