ggml : add version function to get lib version (ggml/1286)

* ggml : add version function to get lib version

This commit adds a function `ggml_version()` to the ggml library that
returns the version of the library as a string.

The motivation for this is that it can be useful to be able to
programmatically check the version of the ggml library being used.

Usage:
```c
printf("GGML version: %s\n", ggml_version());
```
Output:
```console
GGML version: 0.0.2219
```

* ggml : add ggml_commit()

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

ggml/include/ggml.h

@@ -646,6 +646,9 @@ extern "C" {
 
     // misc
 
+    GGML_API const char * ggml_version(void);
+    GGML_API const char * ggml_commit(void);
+
     GGML_API void    ggml_time_init(void); // call this once at the beginning of the program
     GGML_API int64_t ggml_time_ms(void);
     GGML_API int64_t ggml_time_us(void);