unix: map `ELOOP` to `UV_ELOOP`

Merge remote-tracking branch 'ry/v0.6'

uv.h: add EPERM to errno map to fix regression

EPERM isn't mapped in so chown returns an unknown error. This is a
regression from 0.4.12.

philips:node/ (master*) $ cat chown.js

uv.h: add EPERM to errno map to fix regression

EPERM isn't mapped in so chown returns an unknown error. This is a
regression from 0.4.12.

philips:node/ (master*) $ cat chown.js
var fs = require('fs')
fs.chown("/tmp/foobar", 100, 100, function(er){ console.log(er);})

philips:node/ (master*) $ ls -la /tmp/foobar
total 0
drwxr-xr-x 2 root wheel 68 Jan 24 17:21 .

0.4
---

philips:node/ (master*) $ /usr/local/Cellar/node/0.4.12/bin/node chown.js
{ stack: [Getter/Setter],
arguments: undefined,
type: undefined,
message: 'EPERM, Operation not permitted \'/tmp/foobar\'',
errno: 1,
code: 'EPERM',
path: '/tmp/foobar' }

master
------

philips:node/ (master*) $ ./node chown.js
{ [Error: UNKNOWN, unknown error '/tmp/foobar'] errno: -1, code: 'UNKNOWN', path: '/tmp/foobar' }

AFTER
-----

philips:node/ (master*) $ ./node chown.js
{ [Error: EPERM, operation not permitted '/tmp/foobar'] errno: 49, code: 'EPERM', path: '/tmp/foobar' }

show more ...

import/export streams accross loops

Merge remote-tracking branch 'origin/v0.6'

unix: implement uv_udp_set_multicast_loop()

unix: implement uv_udp_set_ttl()

Add missing UV_EXTERN declarations in uv.h

unix: map `ENAMETOOLONG` to `UV_ENAMETOOLONG`

With tests. Closes #295

unix: add uv_udp_set_broadcast() and uv_udp_set_multicast_ttl()

Add uv_loop_refcount() function, debug tool.

unix: it's legal for dlsym() to return NULL

A symbol name can map to NULL. Check dlerror() to see if a real error happened.

windows: enable pending pipe instances knob

uv_cwd + uv_chdir

Remove incorrect documentation comment.

The callback for uv_close does not have a status parameter.

Note that uv_is_active works on timers.

Fix typos.

Win: get rid of UV_EAINONAME, use UV_ENOENT instead

Bump version to v0.6

Use (void) for a function taking no arguments - fix gcc -Wstrict-prototypes

Fix warning: comma at end of enumerator list

Remove unnecessary errno

Alternative errno strategy

Add UV_ESRCH

Fixes #239.

unix: map EISDIR