File boost-threading.patch of Package boost

--- tools/build/v2/tools/gcc.jam
+++ tools/build/v2/tools/gcc.jam
@@ -770,7 +770,7 @@
         }
     case * :
         {
-        flags gcc OPTIONS <threading>multi : -pthread ;
+        flags gcc OPTIONS <threading>multi : -pthread -D_REENTRANT ;
         flags gcc FINDLIBS-SA : rt ;
         }
     }