Function addhookfunc 

pub fn addhookfunc(n: &str, f: Hookfn) -> i32

Port of int addhookfunc(char *n, Hookfn f) from Src/module.c:948.

C body (c:948-955):

int addhookfunc(char *n, Hookfn f) {
    Hookdef h = gethookdef(n);
    if (h) return addhookdeffunc(h, f);
    return 1;
}