Dev/zephyr file socket

[srberard]

This is still a work in progress, but committing now to make the code available for others who might want to review, test, or build on it while it's still being developed.

Fixes include the following (Zephyr target):

• Improved Socket support
• Fixes to stdout/console output
• Fixes for fstat, fstatat, and unlink
• Code changes to fix numerous build warnings.

This branch still needs to be updated to the latest trunk and validation on non-Zephyr platforms.