whitespace fixup
misc "obvious" signedness fixups with no real downsides
Refactor PRNG code/interfaces in libgdnsd

This bumps the plugin API version to 17 as well and will require
bumping the release version 2.2.0 when the time comes.  This could
have been handled in a backwards-compatible way even at the ABI
level, but (a) beff52ac requires an API version bump + recompile
anyways and (b) the source changes to accomodate this are trivial
for any plugin that needs them.
Remove several compiler warning flags that are implied by others

These are all implied by -Wall, -Wextra, or other remaining flags
in recent gcc and/or clang versions, so there's no need for the
extra clutter.
Add some missing funcattrs in libdmn
Fix AD_GET_PTR() on weird platforms

It looked like it would probably break if some platform had
sizeof(unsigned long) != sizeof(uintptr_t).  This version should
fix that.
Add -Wcast-qual, fix remaining cases that trip it
simplify dname_status()
Add -Wswitch-default, fix cases that trip it
remove bad/pointless uses of restrict

The ones in the args for dname_from_raw() are pointless since the
compiler can deduce this for a static function (they were brought
over from when it used to be an external one).  The one within
encode_rrs_txt is difficult to understand, and thus we're probably
better off removing it than trying to understand it.
Clean up more API stuff since we are incrementing anyways
Misc updates to qa scripts