WL#5041: Eliminate all warnings from server build

Warnings generated by GCC are usually quite significant and we should normally
not allow warnings in our builds.  However, the number of warnings currently
prevents us from using the -Werror flag, which will flag all warnings as errors.

This worklog is about eliminating all warnings from the build so that we can
turn on the -Werror flag in pushbuild and catch potential problems earlier.

- Turn on ``-Werror`` in the normal build scripts under ``BUILD/``
- Eliminate all warnings in the code
- Ensure that ``-Werror`` is turned on in a staging tree under PushBuild
  control and push to this tree
- Eliminate all resulting errors.
- Push the staging tree to the main tree and turn on ``-Werror`` there as well.