zephyr_tzc_escape_msg and zephyr_tzc_deescape_str refactoring

* Move declarations before implementations. Also slightly change `local_zephyr_normalize` signature
* Early return from functions
* Get `strlen(message)` once
* Convert `while` to `for`
* Simplify escaping
* Remove nulling of last char since `newmsg` already initialized to 0's

Testing Done:
Compile.

Reviewed at https://reviews.imfreedom.org/r/434/