Clear ambiguity regarding Int/Real rand()
Clear ambiguity regarding Int/Real rand()

Specify whether the endpoints are included or not when selecting the
pseudo-random number.

References:

- https://github.com/perl6/roast/blob/master/S32-num/rand.t#L13-L30
- https://github.com/MoarVM/MoarVM/blob/master/3rdparty/tinymt/tinymt64.c#L97-L116

Fixes #787.

MasterDuke17/doc,stmuk/doc,jonathanstowe/doc,perl6/doc,dmaestro/doc,jonathanstowe/doc,gfldex/doc,jonathanstowe/doc,gfldex/doc,stmuk/doc,jonathanstowe/doc,jonathanstowe/doc,gfldex/doc,antquinonez/doc,tbrowder/doc,perl6/doc,dmaestro/doc,MasterDuke17/doc,antquinonez/doc,stmuk/doc,tbrowder/doc,antquinonez/doc,perl6/doc,MasterDuke17/doc,stmuk/doc,perl6/doc,tbrowder/doc,antquinonez/doc,perl6/doc,stmuk/doc,MasterDuke17/doc,gfldex/doc,antquinonez/doc,gfldex/doc,dmaestro/doc,dmaestro/doc,dmaestro/doc,tbrowder/doc