ANNOYING COMMIT: add a parse function for every deftac(l) :-(
ANNOYING COMMIT: add a parse function for every deftac(l) :-(

NOTES:
1. the script in the library can now use the full notation in tactics too.
   So far we very very rarely used terms in the script because the scripts
   were very procedural
2. when defining a new tactic, if the programmer wants to use the notation,
   he will have to call parse himself in proper places. Doing that
   systematically leads to a quadratic algorithm because, for example,
   (then HUGE1 HUGE2) would expand to (thenll HUGE1 ... HUGE2 ...) and
   HUGEi would be parsed again and again.

LPCIC/elpi