This reverts commit f3d14bf9.

radius: implemented accounting interim update timeout

updated build system: accel-pptp.conf will be installed as /etc/accel-pptp.conf.dist to prevent user config erasing

radius: introduced dae-server option to configure Dynamic Authorization Extenstion (DM/CoA) instead of dm_coa_secret

       implemented PADO delay

implemented chap-secrets module which reads username,password and ip address from pppd compatible chap-secrets file

updated documentation

radius: implemented mppe support
various improvements and bug fixes

radius: implemented extension Acct-Input-Gigawords, Acct-Output-Gigawords
lcp:    implemented maximum/minimum mtu/mru checks

log: simplified engine
various bug fixes

        and newly introduced -  ip-change, when radius CoA request received,
        also this module manages pppd compatible radattr.pppX files
core:   implemented module 'sigchld' which handles SIGCHLD signal,
        waits child processes to terminate and manages pid terminate handlers