[trans-mem] Fix compilation of libitm with recent gcc

[Patrick Marlier]

Here the error when gcc compiles libitm:

../../../transactional-memory/libitm/aatree.h: In constructor 
‘GTM::aa_node_base::aa_node_base(GTM::aa_node_base::level_type)’:
../../../transactional-memory/libitm/aatree.h:53:16: error: 
list-initializer for non-class type must not be parenthesized [-Werror]

The fix just consists to remove the parenthesis.

Patrick.

Index: aatree.h
===================================================================
--- aatree.h    (revision 178056)
+++ aatree.h    (working copy)
@@ -48,8 +48,8 @@

  public:
   aa_node_base(level_type l = 1)
-    : m_link({ const_cast<aa_node_base *>(&s_nil),
-            const_cast<aa_node_base *>(&s_nil) }),
+    : m_link { const_cast<aa_node_base *>(&s_nil),
+            const_cast<aa_node_base *>(&s_nil) },
       m_level(l)
   { }