Revert "Don't expose unavailable cstdio functions."

Revert "Don't expose unavailable cstdio functions."

Broke builders that emit different diagnostics. e.g.:

error: 'warning' diagnostics seen but not expected:
  Line 13: alias declarations are a C++11 extension
  Line 20: alias declarations are a C++11 extension

This reverts commit ff87813715ec32741ce230dd37c13d0ae6673f9c.