rtapi/syslog-async: import syslog-async-0.2.tar.gz

from http://www.thekelleys.org.uk/syslog-async
this is to get around syslog() blocking and signal handling issues
rtapi/syslog-async: integrate: make C++-proof, add Submakefile
rtapi_msgd: make it use syslog_async()
rtapi_app: make it use syslog_async()
ulapi: delete unused include syslog.h
posix/rtapi_get_clocks: fall back onto clock_gettime() if no TSC available

there might be a TSC equivalent on ARM, but it cannot be used without
enabling in kernel mode. Use this until we know better, or can provide
an option to use a hardware TSC.

Depending on how clock_gettime() is implemented, this may not be a
delay factor any more; glibc on at least x86 and amd64 uses a vDSO call
for this.