Fix PSP_STDIN and PSP_MIN_FD value

[sum2012]

According JPCSP source
https://github.com/jpcsp/jpcsp/blob/bb94cd4f9b211d3efa5519c6f218764be2985589/src/jpcsp/HLE/modules/IoFileMgrForUser.java#L171 Fix #19435

[anr2me]

i see that JPCSP also use the same value, nice find!
So 0-2 are reserved for STDIN, STDOUT, STDERR, similar to most commercial Unix systems where /dev/stdin is symlinked to /dev/fd/0 or /proc/self/fd/0

[hrydgard]

Hm, seems right, nice one - though, I'm wondering if we should add savestate versioning for this - let old states keep the old minimum, and old stdin number. However, given how ID allocation currently works, and that no games actually use stdin as far as I know, I think the risk for problems is probably really small...

I'll have another look at the code soon and probably merge this today.

[hrydgard]

Yeah I can't figure out how this change could possibly break existing savestates, anything, unless a game was silly enough to use > or < on file handles and made assumptions on the results. So let's just go with it as it is, it's clearly right.