Function: qforbits
Section: linear_algebra
C-Name: qforbits
Prototype: GG
Help: qforbits(G,V): return the orbits of V under the action of the group
 of linear transformation generated by the set G, which must stabilize V.
Doc: qforbits(G,V): return the orbits of $V$ under the action of the group
 of linear transformation generated by the set $G$.
 It is assumed that $G$ contains minus identity, and only one vector
 in $\{v, -v\}$ should be given.
 If $G$ does not stabilize $V$, the function return $0$.
