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;
 
diff --git a/lib/Parse/ParseObjc.cpp b/lib/Parse/ParseObjc.cpp
index bd1866f..4e5b672 100644
--- a/lib/Parse/ParseObjc.cpp
+++ b/lib/Parse/ParseObjc.cpp
@@ -1347,15 +1347,15 @@
 ///     objc-protocol-forward-reference
 ///
 ///   objc-protocol-definition:
-///     @protocol identifier
+///     \@protocol identifier
 ///       objc-protocol-refs[opt]
 ///       objc-interface-decl-list
-///     @end
+///     \@end
 ///
 ///   objc-protocol-forward-reference:
-///     @protocol identifier-list ';'
+///     \@protocol identifier-list ';'
 ///
-///   "@protocol identifier ;" should be resolved as "@protocol
+///   "\@protocol identifier ;" should be resolved as "\@protocol
 ///   identifier-list ;": objc-interface-decl-list may not start with a
 ///   semicolon in the first alternative if objc-protocol-refs are omitted.
 Parser::DeclGroupPtrTy 
@@ -2730,7 +2730,7 @@
 }
 
 ///     objc-protocol-expression
-///       @protocol ( protocol-name )
+///       \@protocol ( protocol-name )
 ExprResult
 Parser::ParseObjCProtocolExpression(SourceLocation AtLoc) {
   SourceLocation ProtoLoc = ConsumeToken();