* commands_macros.hh: Change command definition macros to
	keep results between commands.

	* common.hh: Add access to the global result.

	* common_automaton_commands.hh,
	* common_commands.hh: Change command output to
	keep results.

	* getters.hh,
	* getters.hxx: Allow getters to get data from the global
	result.

	* main.cc: Allow internal command sequencing using "\|"

	* pipe.hh: New.
	* pipe.hxx: New.
	* pipe_command_sequence.hh: New.
	* pipe_command_sequence.hxx: New.
	* pipe_getters.hh: New.
	* pipe_getters.hxx: New.
	* pipe_writers.hh: New.
	* pipe_writers.hxx: New.
	Implementation of the internal pipe.  Documentation will be
	provided shortly.

	* ratexp_commands.hh,
	* tdc_commands.cc: Change command output to
	keep results.

	Implementation of internal pipe in taf-kit (See Ticket #93):
	Commands can be sequenced using "\|" in tak-kit binaries.
	Command-line options are specific to their command except
	Timer & Bencher manipulation options (--report-time, --bench,
	--export-time-dot, --export-time-xml), which are global to
	the whole sequence.
	i.e.: --bench will benchmark the whole sequence.  The defect
	described in ticket #104 is also resolved.

	Note: In vcsn-b and vcsn-z, both automata and regular
	expressions keep their internal representation between
	commands.  In vcsn-tdc, both boolean automata and
	transducers do, but there might be issues about
	boolean_transducer namespace not being declared in
	CONTEXT_HEADER.
	The binaries have yet to be extensively tested.