dtrace: support kernels built with RANDOMIZE_BASE

dtrace: support kernels built with RANDOMIZE_BASE

SDT probe addresses were being generated as absolute addresses which
breaks when the kernel may get relocated to a place other than the
default load address.

The solution is to generate the probe locations as an offset relative to
the _stext symbol in the .tmp_sdtinfo.S source file (generated at build
time), so that the actual addresses are processed as relocations when the
kernel boots.

This fix also optimizes the SDT info data (function and probe names) by
using de-duplication since especially with perf probes) many of those
strings are non-unique.

Orabug: 29204005
Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Nick Alcock <nick.alcock@oracle.com>
Tested-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>