Remove @brief commands from doxygen comments, too.

This is a follow-up to r331272.

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

https://reviews.llvm.org/D46290

llvm-svn: 331275
diff --git a/llvm/lib/BinaryFormat/Magic.cpp b/llvm/lib/BinaryFormat/Magic.cpp
index afc217c..5a33958 100644
--- a/llvm/lib/BinaryFormat/Magic.cpp
+++ b/llvm/lib/BinaryFormat/Magic.cpp
@@ -31,7 +31,7 @@
   return Magic.startswith(StringRef(S, N - 1));
 }
 
-/// @brief Identify the magic in magic.
+/// Identify the magic in magic.
 file_magic llvm::identify_magic(StringRef Magic) {
   if (Magic.size() < 4)
     return file_magic::unknown;