Remove many references to ASTContext::getAllocator(), replacing them with calls to the recently added placement new (which uses ASTContext's allocator for memory). Also added ASTContext::Deallocate().

This will simplify runtime replacement of ASTContext's allocator. Keeping the allocator private (and removing getAllocator() entirely) is also goodness.

llvm-svn: 63135
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 016f7b1..983c726 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -405,7 +405,7 @@
   }  
 
   this->~Decl();
-  C.getAllocator().Deallocate((void *)this);
+  C.Deallocate((void *)this);
 #endif
 }