Adding the new sort library.

.gitmodules

@@ -482,3 +482,7 @@
 	path = libs/lexical_cast
 	url = ../lexical_cast.git
 	fetchRecurseSubmodules = on-demand
+[submodule "sort"]
+	path = libs/sort
+	url = ../sort.git
+	branch = master

libs/sort

@@ -0,0 +1 @@
+Subproject commit 7cea8257cbe8e904b06f8d26820e5947134b7ad8