Bug 1452 – std.cstream doc incorrect - imports of stream and stdio are not public

The std.cstream doc says "Both std.c.stdio and std.stream are publicly imported by std.cstream." But in fact both imports are private. Either the doc needs to be changed, or 'public' needs to be added to those imports. I suspect this is a holdover of the change from public default to private default on imports.

std.cstream uses public imports on git HEAD, so this was fixed at some point.