Function: algtensor
Section: algebras
C-Name: algtensor
Prototype: GGD3,L,
Help: algtensor(al1,al2,{flag=3}): tensor product of al1 and al2.
Doc: Given two algebras \var{al1} and \var{al2}, computes their tensor
 product. $\fl$ has the same meaning as in \kbd{alginit}.

 Currently only implemented for cyclic algebras of coprime degree over the same
 center~$K$, and the tensor product is over~$K$.
