Use gs_initData.csInit only to ensure that we call wxEntryStart() once
even if there are multiple calls to wxInitialize() from multiple
threads, but don't keep it locked for the duration of that function as
this is unnecessary and results in -- probably benign in practice, but
still annoying -- warnings from the thread sanitizer about lock order
inversions due to locking csInit first before locking gs_mutexGui in
wxThreadModule::OnInit() and then acquiring csInit again while
gs_mutexGui is still locked in wxUninitialize().
This shouldn't result in any observable changes in behaviour.
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