Update endian.h for AIX/IRIX

Added AIX/IRIX compatibility for endian detection.

ok bcook@ deraadt@ beck@
add asprintf / vasprintf from OpenSSH portable

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produce a error if platform has no arc4random hook

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added dist.sh script - generates tarball

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stub win32 issetugid implementation

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add sys/mman.h shim to define MAP_ANON if needed

thanks to kinichiro for pointing this out

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