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/Support/MemoryBuffer.cpp b/llvm/lib/Support/MemoryBuffer.cpp
index 9139ba4..fe04bb6 100644
--- a/llvm/lib/Support/MemoryBuffer.cpp
+++ b/llvm/lib/Support/MemoryBuffer.cpp
@@ -163,7 +163,7 @@
 //===----------------------------------------------------------------------===//
 
 namespace {
-/// \brief Memory maps a file descriptor using sys::fs::mapped_file_region.
+/// Memory maps a file descriptor using sys::fs::mapped_file_region.
 ///
 /// This handles converting the offset into a legal offset on the platform.
 template<typename MB>