Make name of vmd submodule be consistent with everything else.

.gitmodules

@@ -498,7 +498,7 @@
 	path = libs/endian
 	url = ../endian.git
 	fetchRecurseSubmodules = on-demand
-[submodule "libs/vmd"]
+[submodule "vmd"]
 	path = libs/vmd
 	url = ../vmd.git
 	fetchRecurseSubmodules = on-demand