ppp: update to version 2.4.8.git-2020-05-25
ddd57c2 pppd: Add lcp-echo-adaptive option
c319558 pppd: Handle SIGINT and SIGTERM during interrupted syscalls (#148)
0bc11fb Added missing options to manual pages. (#149)
b1fcf16 Merge branch 'monotonic-time' of https://github.com/themiron/ppp
c78e312 pppd: linux: use monotonic time if possible
Remove patch 121-debian_adaptive_lcp_echo as patch is upstream accepted
Remove patch 206-compensate_time_change.patch as timewrap issues are
solved by a patch making use of monotonic time
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>