Re: why md5.toMD5 violate {. noSideEffect .} pragma? and why modify var T not violate it?

[mratsim]

I'm not to sure why MD5 use copyMem and zeroMem and also conversion to 
`cstring`.

Note that the module was written mostly in 2010: 
[https://github.com/nim-lang/Nim/commits/version-1-0/lib/pure/md5.nim](https://github.com/nim-lang/Nim/commits/version-1-0/lib/pure/md5.nim)

It wouldn't look the same now and we can certainly modify it to be nosideeffect.