New feature: SRANDOM as in bash 5.1+, with upper bound

[McDutchie]

SRANDOM is a secure random number generator. It uses the OS implementation of arc4random(3) or, absent that, an integrated OpenBSD-based version that uses the ChaCha20 cipher. An upper bound can be set by assigning its value to SRANDOM; subsequent numbers will be uniformly distributed between 0 and the value of the upper bound minus one, in a way that avoids modulo bias.

I'd like everyone to play with and test this new feature and report back – well, those of you who keep up with the dev branch, that is. It's on the dev branch only and will be in ksh 93u+m/1.1 and up. See 00b296c for all the info.

I am particularly interested in knowing whether this compiles and runs on more obscure systems (Solaris, QNX, AIX, HP-UX, Cygwin) as I am currently unable to test any of these due to broken hardware and lack of access.

[JohnoKing]

I can confirm that SRANDOM compiles and functions just fine on Cygwin (Windows 11), as well as Haiku, illumos and *BSD.

[McDutchie]

Excellent, thank you.

[JohnoKing]

While testing a different issue I stumbled across a bug in SRANDOM that occurs on Cygwin, but not Linux (filed as #711).