Distinguish script-based fresh ids with differing args

f4db03ee started memoizing the fresh identifiers generated by scripts to keep them consistent across different rules. But it did not account for the script producing a different result depending on the values of inherited metavariables passed to it as explicit arguments.

Let’s memoize the script results in a hash map, one fresh name per each different argument list.

Fixes: https://github.com/coccinelle/coccinelle/issues/283

Signed-off-by: Jan Tojnar jtojnar@gmail.com