dtrace: DT_SYSTRACE should not depend on FTRACE_SYSCALLS.

dtrace: DT_SYSTRACE should not depend on FTRACE_SYSCALLS.

The systrace provider depends on the FTRACE_SYSCALLS kernel feature.
The systrace provider is actually called syscall on Solaris, so it has been
renamed on the Linux side (i.e. it registers itself as syscall).
Added some debug statements to track probe searches better.
The probes/probematch ioctl handling should return -ESRCH when the last hit
has been returned already.

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>