Logging buffer implemented by skip list

Use skip list to implement a log buffer,
log sentences will be inserted into this buffer
once the log print function is called. the
buffer will be dumped when GNSS process
crash/killed or send SIGUSR1 signal manually.

Change-Id: I5e23cdf30c263fa59108070c9dbfd95c49c2e9b6
CRs-Fixed: 2571326
10 files changed