Fix Recursive_Mkdir if path doesn't end with "/"

Somewhat surprisingly, Recursive_Mkdir(TWRES "customlanguages")
did not create the "customlanguages" directory because it expected
a trailing slash. Fixed by rewriting the loop to be more like
Create_Dir_Recursive.

Also fixed error handling for the final directory, and fixed incorrect
return value handling for "mkdir" ORS command.

Change-Id: I1ab418ddda695cbb595a9db2817f00fc7b171f51