[ORC] Rename ORC layers to make the "new" ORC layers the default.

This commit adds a 'Legacy' prefix to old ORC layers and utilities, and removes
the '2' suffix from the new ORC layers. If you wish to continue using the old
ORC layers you will need to add a 'Legacy' prefix to your classes. If you were
already using the new ORC layers you will need to drop the '2' suffix.

The legacy layers will remain in-tree until the new layers reach feature
parity with them. This will involve adding support for removing code from the
new layers, and ensuring that performance is comperable.

llvm-svn: 344572
diff --git a/llvm/lib/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.cpp b/llvm/lib/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.cpp
index e84295c..fa57414 100644
--- a/llvm/lib/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.cpp
@@ -76,14 +76,14 @@
 namespace llvm {
 namespace orc {
 
-RTDyldObjectLinkingLayer2::RTDyldObjectLinkingLayer2(
+RTDyldObjectLinkingLayer::RTDyldObjectLinkingLayer(
     ExecutionSession &ES, GetMemoryManagerFunction GetMemoryManager,
     NotifyLoadedFunction NotifyLoaded, NotifyEmittedFunction NotifyEmitted)
     : ObjectLayer(ES), GetMemoryManager(GetMemoryManager),
       NotifyLoaded(std::move(NotifyLoaded)),
       NotifyEmitted(std::move(NotifyEmitted)) {}
 
-void RTDyldObjectLinkingLayer2::emit(MaterializationResponsibility R,
+void RTDyldObjectLinkingLayer::emit(MaterializationResponsibility R,
                                      VModuleKey K,
                                      std::unique_ptr<MemoryBuffer> O) {
   assert(O && "Object must not be null");
@@ -153,7 +153,7 @@
       });
 }
 
-Error RTDyldObjectLinkingLayer2::onObjLoad(
+Error RTDyldObjectLinkingLayer::onObjLoad(
     VModuleKey K, MaterializationResponsibility &R, object::ObjectFile &Obj,
     std::unique_ptr<RuntimeDyld::LoadedObjectInfo> LoadedObjInfo,
     std::map<StringRef, JITEvaluatedSymbol> Resolved,
@@ -196,7 +196,7 @@
   return Error::success();
 }
 
-void RTDyldObjectLinkingLayer2::onObjEmit(VModuleKey K,
+void RTDyldObjectLinkingLayer::onObjEmit(VModuleKey K,
                                           MaterializationResponsibility &R,
                                           Error Err) {
   if (Err) {