Let --trace, --display, and --profile take an optional fd.
	This patch is ugly, with a lot of code duplication...
	I'll improve it late, but be my guest if you feel like.
	* src/Opt.hs (Flag): Replace Trace and Display with TraceFd and
	DisplayFd.
	Adjust all the code.
	(profilefdm displayfd, tracefd): New.
	(extract): Adjust.
	* src/VMMonad.hs (setDisplayHandle, setTraceHandle)
	(getDisplayHandle, getTraceHandle): New.
	* src/Main.hs: Import and use them.
	* src/Trace.hs (hwarn): New.
	(averbose): Use it.
	* doc/havm.texi (Invoking havm): Adjust.