ktracing: TraceOutput::PrintStackTrace(): Fix duplication
X86VMTranslationMapPAE: Extend kernel tracing

* Beside the physical address also print the PTE flags.
* Also trace Protect(), ClearFlags(), ClearAccessedAndModified().
FD kernel tracing: Capture kernel-only stack traces

* When exec()'ing we'd otherwise get (harmless but annoying) messages
  from vm_page_fault(). With syscall tracing enabled we can get userland
  stack traces anyway.
* Simplify by using TRACE_ENTRY_SELECTOR().