* src/common.hh,
	* src/main.cc:
	Add two command-line options to taf-kit binaries.
	The global timer in taf-kit can now be exported in
	DOT format using --export-time-dot and in XML format
	using --export-time-xml.

	Additionally, --report-time now takes the verbose
	level of the report as an optional parameter.

	See ../include/vaucanson/misc/timer.hh for
	documentation.