fix doxygen brief in subzero header files

src/IceLiveness.cpp

Index: src/IceLiveness.cpp
diff --git a/src/IceLiveness.cpp b/src/IceLiveness.cpp
index 25cfd09d70d6868c3ce45cf4202bd895deedd5b5..2bfa624d57cf03f5c3855648871e9b30291a7e7f 100644
--- a/src/IceLiveness.cpp
+++ b/src/IceLiveness.cpp
@@ -8,14 +8,15 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file provides some of the support for the Liveness class. In
-/// particular, it handles the sparsity representation of the mapping between
-/// Variables and CfgNodes. The idea is that since most variables are used only
-/// within a single basic block, we can partition the variables into "local" and
-/// "global" sets. Instead of sizing and indexing vectors according to
-/// Variable::Number, we create a mapping such that global variables are mapped
-/// to low indexes that are common across nodes, and local variables are mapped
-/// to a higher index space that is shared across nodes.
+/// \brief Provides some of the support for the Liveness class.
+
+/// In particular, it handles the sparsity representation of the mapping
+/// between Variables and CfgNodes. The idea is that since most variables are
+/// used only within a single basic block, we can partition the variables into
+/// "local" and "global" sets. Instead of sizing and indexing vectors according
+/// to Variable::Number, we create a mapping such that global variables are
+/// mapped to low indexes that are common across nodes, and local variables are
+/// mapped to a higher index space that is shared across nodes.
 ///
 //===----------------------------------------------------------------------===//