dtrace: restructuring to support DTrace on multiple architectures

dtrace: restructuring to support DTrace on multiple architectures

Restructure the DTrace modules code to facilitate supporting ultiple
architectures (rather than just x86_64).

- The assembler implementation of support functions is now in a file
  named dtrace_asm_<arch>.S and arch-specific aspects are found in
  dtrace_isa_<arch>.c.  The SDT provider requires an arch-specific
  portion of code as well (in sdt_<arch>.c).

- The number of frames to skip for specific probes has been updated
  to be more accurate (mistakes in this area were found during code
  review).

- The mechanism for direct calling the test probe in dt_test_probe()
  has been updated to work around compiler warnings.

- Removed dtrace_modload and dtrace_modunload.  They were expected to
  be needed for multi-arch support but it turns out that was not the
  case.

- Add conditionals to not try to build anything that relates to providers
  not necessarily being supported on all platforms.

- Various fixes for varable datatype issues that were not noticed on
  x86 because they mapped to the same or similar numeric datatypes.

- Pass the dtrace_mstate_t struct to dtrace_getstackdepth() to support
  the limitation that memory allocation cannot be done from probe
  context.  The dtrace_getstackdepth() function uses the dtrace_mstate_t
  information to obtain a scratch area of memory to use as temporary
  storage for PCs in the processing of dtrace_stacktrace().

- Handle the fact that on x86, the user sp for the current task can be
  obtained using current_user_stack_pointer() whereas other platforms
  use user_stack_pointer(current_pt_regs).

- Support that fact that the current instruction pointer is not always
  an 'ip' member of the pt_regs struct.  Always obtain the value of
  the instruction pointer using the instruction_pointer(regs function.

- Support the use of asm/dtrace_syscall.h to list the system calls
  that are implemented using an assembler stub.

- Ensure that membar functions use the SMP-versions.

- Clean up byte order conditionals.

- Remove dead code.

- Ensure needed header files are explicitly included.

- Update copyright statements.

Orabug: 20262965

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Acked-by: Nick Alcock <nick.alcock@oracle.com>