llama : add ggml version and commit functions

[danbev]

This commit adds functions that expose the ggml-version and ggml commit in llama.h.

The motivation for this is that allow users of llama.cpp to be able to get the version of ggml that is in use.

Note: I've opened ggml-org/ggml#1336 for the actual changes to ggml as it was easier to make the changes there and it also required an addition to the ggml/scripts directory which is not available in this repo.

Refs: ggml-org/ggml#1333