Improve performance of network receive code

[octo]

This ticket is being written ex-post-facto, as a means of referencing work that has already been done. It is also here to serve as a reference for any bugs that may arise, until this work is considered 100% complete and bug-free.

The network receive code in LogicMail is one of the last pieces of code leftover from the Mail4ME project. It is highly inefficient, as it reads data from the socket one byte at a time. This code needs to be rewritten to read data in larger chunks.

The following changesets should refer to this ticket: [679], [680], [685].