Function: msgetsign
Section: modular_symbols
C-Name: msgetsign
Prototype: lG
Help: msgetsign(M): M being a full modular symbol space, as given by msinit, return its sign.
Doc: $M$ being a full modular symbol space, as given by \kbd{msinit}, return
 its sign: $\pm1$ or 0 (unset).
 \bprog
 ? M = msinit(11,4, 1);
 ? msgetsign(M)
 %2 = 1
 ? M = msinit(11,4);
 ? msgetsign(M)
 %4 = 0
 @eprog
