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/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 2ad19a7..f9b8889 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -480,7 +480,7 @@
   return IsRelocatable && Value.isAbsolute();
 }
 
-/// \brief Helper method for \see EvaluateSymbolAdd().
+/// Helper method for \see EvaluateSymbolAdd().
 static void AttemptToFoldSymbolOffsetDifference(
     const MCAssembler *Asm, const MCAsmLayout *Layout,
     const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A,
@@ -537,7 +537,7 @@
   A = B = nullptr;
 }
 
-/// \brief Evaluate the result of an add between (conceptually) two MCValues.
+/// Evaluate the result of an add between (conceptually) two MCValues.
 ///
 /// This routine conceptually attempts to construct an MCValue:
 ///   Result = (Result_A - Result_B + Result_Cst)