Since the upstream for cddl code is now illumos not sun, mechanically
convert all sun #ifdef's to illumos #ifdef's which have been used in all
newer code for some time.
Also do a manual pass to correct the use if #ifdef comments as per style(9)
as well as few uses of #if defined(__FreeBSD__) vs #ifndef illumos.
MFC after: 1 month
Sponsored by: Multiplay
To quote original Illumos ticket:
libctf thinks that any ELF file containing more than 65536 sections is
corrupt, because it doesn't understand the SHN_XINDEX magic.
Illumos DTrace issues:
4005 libctf can't deal with extended sections