Resolve missing C function prototypes

- Enable "-Wmissing-prototypes" compiler warning flag in the CMake and Bazel build scripts to catch missing prototypes. Additionally, enable "-Wstrict-prototypes" option.

- Expose missing prototypes in the public API.

- Resolve conflicting prototypes by aligning the definition to the declaration.

Signed-off-by: Jakub Sujak <jakub.sujak@arm.com>

Approved-by: Emil Ohlsson <emil.ohlsson@arm.com>