Remove \brief commands from doxygen comments.

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

Differential Revision: https://reviews.llvm.org/D46290

llvm-svn: 331272
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 36f1661..b51e842 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -1634,7 +1634,7 @@
   return nullptr;
 }
 
-/// \brief Build up a vector of value/power pairs factoring a product.
+/// Build up a vector of value/power pairs factoring a product.
 ///
 /// Given a series of multiplication operands, build a vector of factors and
 /// the powers each is raised to when forming the final product. Sort them in
@@ -1699,7 +1699,7 @@
   return true;
 }
 
-/// \brief Build a tree of multiplies, computing the product of Ops.
+/// Build a tree of multiplies, computing the product of Ops.
 static Value *buildMultiplyTree(IRBuilder<> &Builder,
                                 SmallVectorImpl<Value*> &Ops) {
   if (Ops.size() == 1)
@@ -1716,7 +1716,7 @@
   return LHS;
 }
 
-/// \brief Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
+/// Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*...
 ///
 /// Given a vector of values raised to various powers, where no two values are
 /// equal and the powers are sorted in decreasing order, compute the minimal