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/Frontend/PCHContainerOperations.cpp b/clang/lib/Frontend/PCHContainerOperations.cpp
index eebebf3..340e8ce 100644
--- a/clang/lib/Frontend/PCHContainerOperations.cpp
+++ b/clang/lib/Frontend/PCHContainerOperations.cpp
@@ -25,7 +25,7 @@
 
 namespace {
 
-/// \brief A PCHContainerGenerator that writes out the PCH to a flat file.
+/// A PCHContainerGenerator that writes out the PCH to a flat file.
 class RawPCHContainerGenerator : public ASTConsumer {
   std::shared_ptr<PCHBuffer> Buffer;
   std::unique_ptr<raw_pwrite_stream> OS;