syscall: document that documentation is platform specific

[gopherbot]

by efairlight:

The syscall package is highly platform specific and the documentation seems to be
generated only for the platform the generator is running on (amd64-linux in the case of
http://tip.golang.org/pkg/syscall/ apparently). This leads to a lack of mention for any
other platform's functions, such as Exchangedata on Darwin, which is however available
on that platform.

Furthermore the documentation doesn't describe what's available on which platform, which
would be highly useful.

[gopherbot]

Comment 1 by lost.goblin:

AFAIK use of the syscall package is at least somewhat discouraged (among other things
code using it is inherently unportable), and I think in part the lack of documentation
is to discourage users.
Perhaps what would help is to document this situation more clearly, and explain under
what circumstances is recommended to use or not use the syscall package.

[rsc]

Comment 2:

We should at least note in the doc comment that things vary by system
and that godoc only shows the docs for the system it is running on.

[rsc]

Comment 3:

Labels changed: added priority-later, removed priority-triage.

Status changed to Accepted.

[rsc]

Comment 4:

Labels changed: added go1.1.

[rsc]

Comment 5:

Labels changed: added size-s.

[rsc]

Comment 6:

Labels changed: added suggested.

[minux]

Comment 7:

This issue was closed by revision 39835b4.

Status changed to Fixed.