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/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 2740c17..96d74b1 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -189,7 +189,7 @@
   return RValue::get(Result);
 }
 
-/// @brief Utility to insert an atomic cmpxchg instruction.
+/// Utility to insert an atomic cmpxchg instruction.
 ///
 /// @param CGF The current codegen function.
 /// @param E   Builtin call expression to convert to cmpxchg.
@@ -320,7 +320,7 @@
   return CGF.EmitCall(E->getCallee()->getType(), callee, E, ReturnValueSlot());
 }
 
-/// \brief Emit a call to llvm.{sadd,uadd,ssub,usub,smul,umul}.with.overflow.*
+/// Emit a call to llvm.{sadd,uadd,ssub,usub,smul,umul}.with.overflow.*
 /// depending on IntrinsicID.
 ///
 /// \arg CGF The current codegen function.
@@ -3667,7 +3667,7 @@
   return ConstantInt::get(Ty, neg ? -SV : SV);
 }
 
-// \brief Right-shift a vector by a constant.
+// Right-shift a vector by a constant.
 Value *CodeGenFunction::EmitNeonRShiftImm(Value *Vec, Value *Shift,
                                           llvm::Type *Ty, bool usgn,
                                           const char *name) {