rework the configure script now it resembles less oconfigure and more the configure scripts I'm using in my recent projects. I'd argue it's more easy to use it.

drop landlock/seccomp and capsicum support it reached a point where this stuff is not maintenable. I'd like to move forward with gmid, but the restriction of capsicum and the linux environment at large that make landlock unusable (how can you resolve DNS portably when under landlock?) -and don't get me started on seccomp- makes it impossible for me to do any work. So, I prefer removing the crap, resuming working on gmid by cleaning stuff and consolidating the features, improving various things etc... and then eventually see how to introduce some sandboxing again on other systems. Patches to resume sandboxing are, as always, welcome!

add tests and compat for setresuid and setresgid

add memmem compat

rework `make dist'