Merge remote-tracking branch 'origin/master' into rework-1

Conflicts:
	debian/configure
	debian/control.in
	scripts/.gitignore
	src/.gitignore
	src/Makefile
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.
ulapi: delete unused include syslog.h
rtapi_app: make it use syslog_async()
rtapi_msgd: make it use syslog_async()
rtapi/syslog-async: integrate: make C++-proof, add Submakefile