radius: fixed incorrect handling when socket read failed with error other than EAGAIN (thanks to GlooM)

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

        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

log: implemented log_file logging target with per-user/per-session support

radius: implemented PAP authorization
radius: implemented IP assigning
triton: implemented userspace context switching
and other stuff