'Step until next \'call\' instruction in specific memory range
Usage:
MYNAME [keyword] [mapname1,mapname2]'

def nextcall(self, *arg):

    (keyword, mapname) = normalize_argv(arg, 2)
    if keyword:
        self.stepuntil(('call.*%s' % keyword), mapname)
    else:
        self.stepuntil('call', mapname)
    return
