Fixes #1869.

fs.readdir() on file should raise ENOTDIR, not UNKNOWN.

Fixes #1857

Fixes #1706.

This removes one of the three build systems. CMake has never been officially
supported and is not updated with WAF and GYP. WAF itself is considered
legacy and will be removed once the GYP system is feature complete on
Unixes. GYP is used currently on Windows/MSVS.

This reverts commit 9bbca991.

Not stable enough.
- Windows snapshot linking broken
- Linux crash on ./node_g test/simple/test-stream-pipe-multi.js

This reverts commit 56e6952e.