platform-encoding branch

[Peter Lobsinger]

The purpose platform-encoding branch is to lay some groundwork for
managing encodings on different platforms.

The underlying assumption used is that a platform uses 1 encoding for
its various interfaces (argv, paths, environment variables, etc). A
new encoding alias, "platform", has been added to be used for
encoding/decoding strings coming from or going to such interfaces.

So far, a generic and linux-specific implementation of the
platform-specific support code has been implemented and the new
functionality has been used to support argv handling and environment
variables.