Function: mfpow
Section: modular_forms
C-Name: mfpow
Prototype: GL
Help: mfpow(F,n): compute F^n
Doc: Compute $F^{n}$, where $n$ is an integer and $F$ is a generalized modular
 form:
 \bprog
 ? G = mfpow(mfEk(4), 3);  \\ E4^3
 ? mfcoefs(G, 4)
 %2 = [1, 720, 179280, 16954560, 396974160]
 @eprog
