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/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index f3b3ed0..b3607ca 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -2305,7 +2305,7 @@
     getParamDecl(0)->getType()->isRValueReferenceType();
 }
 
-/// \brief Determine whether this is a copy or move constructor.
+/// Determine whether this is a copy or move constructor.
 bool CXXConstructorDecl::isCopyOrMoveConstructor(unsigned &TypeQuals) const {
   // C++ [class.copy]p2:
   //   A non-template constructor for class X is a copy constructor