Progress: Improve thread support across programs and update threaded usage.

Progress: Improve thread support across programs and update threaded usage.

Enable the threaded signal handled consistently across all programs that are currently migrated (see commit 9e0529297bfdb1529be685eacd3ca5784ea8e946).

Improve the thread configuration to make it easier to enable or disable thread support.

Add documentation regarding the build modes supported in each of the build settings files.

Update the build scripts to better handle the now additional build modes.
The build scripts now use braces everywhere.
Doing this should make it easier to be compatible with other scripting engines such as ZSH.