This change is required to use the C++ tr1 headers only with libstdc++, as they
are not in C++11.
--- config.h.in.orig	2013-10-20 20:37:35.000000000 +0300
+++ config.h.in	2013-10-20 20:38:41.000000000 +0300
@@ -353,7 +353,8 @@
 
 // TR1 regex not supported in GCC <= 4.5
 #ifndef LYX_USE_TR1
-#  if __GNUC__ == 4 
+#  include <ciso646>
+#  if __GNUC__ == 4 && !defined(_LIBCPP_VERSION)
 #    define LYX_USE_TR1
 #  endif
 #endif