Import of Interval library

[SVN r16980]

.gitmodules

@@ -178,6 +178,10 @@
 	path = libs/statechart
 	url = ../statechart.git
 	fetchRecurseSubmodules = on-demand
+[submodule "interval"]
+	path = libs/numeric/interval
+	url = ../interval.git
+	fetchRecurseSubmodules = on-demand
 [submodule "inspect"]
 	path = tools/inspect
 	url = ../inspect.git

libs/numeric/interval

@@ -0,0 +1 @@
+Subproject commit 21e378f40b250205a086ef202d6d602e8e4f6bcf