Replace use of new Buffer() (e.g. with Buffer.alloc())

[jacobq]

It looks like here and here this code is using new Buffer() to create a Buffer object. However, current versions of node have a newer API for this, and in 10.x one will see a deprecation warning like "[DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.".

This affects downstream project as well, e.g. yarnpkg/yarn#5477

[runk]

Fixed in v0.7.0