nb : do not work for lv4/ec mode

'-' replaced by 'm', '.' by 'd',
(see "correct_num_string" in LicDump.ml)

constants that  are not  on the base  clock, add the  suitable "when"
statement if it was not present  in the source code (the lic (and the
ec/lv4) backend  does not  perform such kind  of clock  inference for
constants.