Remove \brief commands from doxygen comments.

This is similar to the LLVM change https://reviews.llvm.org/D46290.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

for i in $(git grep -l '\@brief'); do perl -pi -e 's/\@brief //g' $i & done
for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46320

llvm-svn: 331834
diff --git a/clang/lib/Sema/CodeCompleteConsumer.cpp b/clang/lib/Sema/CodeCompleteConsumer.cpp
index d012e55..70b3189 100644
--- a/clang/lib/Sema/CodeCompleteConsumer.cpp
+++ b/clang/lib/Sema/CodeCompleteConsumer.cpp
@@ -621,7 +621,7 @@
   }
 }
 
-/// \brief Retrieve the effective availability of the given declaration.
+/// Retrieve the effective availability of the given declaration.
 static AvailabilityResult getDeclAvailability(const Decl *D) {
   AvailabilityResult AR = D->getAvailability();
   if (isa<EnumConstantDecl>(D))
@@ -683,7 +683,7 @@
     Availability = CXAvailability_NotAccessible;
 }
 
-/// \brief Retrieve the name that should be used to order a result.
+/// Retrieve the name that should be used to order a result.
 ///
 /// If the name needs to be constructed as a string, that string will be
 /// saved into Saved and the returned StringRef will refer to it.