std::rt::uv::net: Handle `read_start` error

cc #9605
std::rt: Add NotConnected to IoErrorKind
rt::io::net::tcp: Fix eof_twice tests on Win32

cc #8811
auto merge of #9721 : klutzy/rust/uv-net-read-fix, r=alexcrichton

See #9605 for detailed information.

This also fixes two tests of #8811.
Added comments to public functions in num.rs.

Copied existing comments from other files, and added comments to
functions that did not have existing comments available.
auto merge of #9585 : vky/rust/num-docs, r=alexcrichton

Copied existing comments from other files, and added comments to functions that did not have existing comments available. 

cc #7511
support for GNU configure syntax
use --mandir option