Fixup r331049 (FileSpec auto-normalization)

A typo in the patch (using syntax instead of m_syntax) resulted in the
normalization not working properly for windows filespecs when the syntax
was passed as host-native. This did not affect the unit tests, as all of
those pass an explicity syntax, but failed gloriously when running the
full test suite.

I also fix an expectation in an lldb-mi test, which was now failing
because it was expecting a path to be echoed verbatim, but we were now
normalizing it.

As a drive-by, this also fixes the default-in-fully-covered-switch
warning and removes an unused argument from the NeedsNormalization
function.

llvm-svn: 331172