Function: centerlift
Section: conversions
C-Name: centerlift0
Prototype: GDn
Help: centerlift(x,{v}): centered lift of x. Same as lift except for
 integermods
Description: 
 (pol):pol	centerlift($1)
 (vec):vec	centerlift($1)
 (gen):gen	centerlift($1)
 (pol, var):pol	centerlift0($1, $2)
 (vec, var):vec	centerlift0($1, $2)
 (gen, var):gen	centerlift0($1, $2)

