Adds any calls to executables contained in the specified module.

def _module_callers(parser, modname, result):
    """Adds any calls to executables contained in the specified module.
    """
    if modname in result:
        #We have already processed this module.
        return
    
    module = parser.get(modname)
    mresult = {}
    if module is not None:
        for xname, xinst in module.executables():
            _exec_callers(xinst, mresult)
        result[modname] = mresult
        
        for depkey in module.dependencies:
            depmod = depkey.split('.')[0].lower()
            _module_callers(parser, depmod, result)