bugfix and documentation update

Documentation update: Debian dependencies added
Fix missing ‘socklen_t’ reference:
Scanning dependencies of target log_pgsql
[ 72%] Building C object accel-pppd/logs/CMakeFiles/log_pgsql.dir/log_pgsql.c.o
In file included from /home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_session.h:4:0,
                 from /home/vagrant/wisp/builds/accel-ppp/accel-pppd/logs/log_pgsql.c:11:
/home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_net.h:6:52: error: unknown type name ‘socklen_t’
  int (*connect)(int sock, const struct sockaddr *, socklen_t len);
                                                    ^
/home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_net.h:7:49: error: unknown type name ‘socklen_t’
  int (*bind)(int sock, const struct sockaddr *, socklen_t len);
                                                 ^
/home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_net.h:10:93: error: unknown type name ‘socklen_t’
  ssize_t (*recvfrom)(int sock, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);
                                                                                             ^
/home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_net.h:12:104: error: unknown type name ‘socklen_t’
  ssize_t (*sendto)(int sock, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);
                                                                                                        ^
/home/vagrant/wisp/builds/accel-ppp/accel-pppd/include/ap_net.h:14:76: error: unknown type name ‘socklen_t’
  int (*setsockopt)(int sockfd, int level, int optname, const void *optval, socklen_t optlen);
                                                                            ^
make[2]: *** [accel-pppd/logs/CMakeFiles/log_pgsql.dir/log_pgsql.c.o] Error 1
make[1]: *** [accel-pppd/logs/CMakeFiles/log_pgsql.dir/all] Error 2
make: *** [all] Error 2
xebd / accel-ppp

bugfix and documentation update #2
