Update libuv to 1.6.0

[dbkaplun]

This new version of libuv fixes one particular issue that made the TTY completely unusable on OSX since Node 0.11.13. See libuv/libuv#304. It would be great if libuv could be upgraded to 1.6.0 with the next release of Node!

[Fishrock123]

Note: uv@1.6.1 is out (but only fixes an issue with uv_os_homedir on windows xp)

[cjihrig]

The Windows XP fix is in 1.6.0. The 1.6.1 release actually fixes an issue with FreeBSD, where huge amounts of memory were being allocated by uv_os_homedir().

[misterdjules]

@dbkaplun Thank you for the request 👍 It's already tracked by #25475 which is scheduled to be shipped with node v0.12.5, so I'll close it as a duplicate of that PR.