Documentation cleanup, fixing Doxygen markup. Mostly this avoids common terms
such as "protocol" and "expression" being implicitly turned into links to
mistakenly-generated Doxygen pages:
- Escaping @ symbols when Doxygen would otherwise incorrectly interpret them;
- Escaping # symbols when they're not intended as explicit Doxygen link 
  requests, such as when discussing preprocessor directives;
- In one odd case, unescaping @ in @__experimental_modules_import, because
  Doxygen wrote '\@' to the output in that case, causing the example in the
  description of ImportDecl to be wrong; and
- Fixing a typo: @breif -> @brief.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158299 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGObjCRuntime.h b/lib/CodeGen/CGObjCRuntime.h
index ccf4d4d..135a080 100644
--- a/lib/CodeGen/CGObjCRuntime.h
+++ b/lib/CodeGen/CGObjCRuntime.h
@@ -179,7 +179,7 @@
                            const ObjCMethodDecl *Method = 0) = 0;
 
   /// Emit the code to return the named protocol as an object, as in a
-  /// @protocol expression.
+  /// \@protocol expression.
   virtual llvm::Value *GenerateProtocolRef(CGBuilderTy &Builder,
                                            const ObjCProtocolDecl *OPD) = 0;