Continued adding "--skeleton" switch.

Continued adding "--skeleton" switch.

Output input data to a separate file (otherwize we'll have to
keep all generated data in memory, cause output has a complex
structure and cannot be written to file until it's fully
generated)

This reduces memory usage significantly (so that there remain no
memory consumption problems with "--skeleton" switch). However
on some files re2c generated too much data, e.g. case-insensitive
strings:

/*!re2c
	'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' {}
*/

Exponential growth is a bad thing; must deal with it somehow.
Time grows exponentially as well, of course.