Moved from joyent/libuv#468

@isaacs said:

Regarding: nodejs/node-v0.x-archive#2857

It'd be lovely if there was a way to call a uv_* version of the pwnam family of functions. See man 3 pwnam.

This is needed to reliably and quickly get the home directory path. The home directory path is needed by a lot of node modules, but in some environments the $HOME environment variable is not defined. This can make all kinds of things fail as most code depend on it being defined. The same applies for getting the username of the current user, which is also currently slow and convoluted.