Improve LOOP REPEAT N for constant-foldable N.
Remove reference to nonexistent function
Don't insert @BODY thrice in DO-PACKED-TNS
Parameterize the magic number in Martin's former 'life' patch

(Courtesy originally of Nikodemus)
The default remains 10, but more can help. A spectacularly slow compile-file
went from 1.5 minutes down to 30 seconds by raising this.
It is prudent to change this only around specific files though,
if the remark about possible non-convergence in finite time is to be believed.