The iOS simulator version set via the ‘OS’ flag of the -destination command line parameter should not override the SDK version set via -sdk parameter.
Re-added previously removed code to ensure a version-less SDK name passed to -sdk is automatically mapped to the latest version available of that SDK. [see issue #399]
Fixes 'unrecognized selector' crash when running test cases on iOS 5.0 due to some SenTestKit methods not being implemented on that version [issue #334]