This patch caused at least the following test failures:
1744(normal)
ghci028(ghci)
unicode001(normal)
and additionally made the stage3 build fail.
A little more validation please!
I didn't find the exact cause of the failure yet, but it appears that
the Lexer is miscompiled in some strange way. If any of {Encoding,
StringBuffer, or Lexer} are compiled without -O, the problem goes
away.