Addition of the main command

the command "gluelang" is added.
Support of "file variable"

The following description is supported.

	file f = cat hoge
	cat $f

This description is equivalent to the following bash script

	cat hoge > /tmp/$$-file
	cat /tmp/$$-file
Support of string
Set the output position of the main block

The main block is put at the bottom of a script
with this modification.
Support of guards and here-docments.