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/SemaPseudoObject.cpp b/clang/lib/Sema/SemaPseudoObject.cpp
index 9887977..4484e9b 100644
--- a/clang/lib/Sema/SemaPseudoObject.cpp
+++ b/clang/lib/Sema/SemaPseudoObject.cpp
@@ -253,7 +253,7 @@
     virtual ExprResult buildGet() = 0;
     virtual ExprResult buildSet(Expr *, SourceLocation,
                                 bool captureSetValueAsResult) = 0;
-    /// \brief Should the result of an assignment be the formal result of the
+    /// Should the result of an assignment be the formal result of the
     /// setter call or the value that was passed to the setter?
     ///
     /// Different pseudo-object language features use different language rules