[php-src] Issue #21431: GD extension phpinfo shows libJPEG Version unknown for libJPEG 10

Issue: https://github.com/php/php-src/issues/21431
Author: rainerjung

### Description

File ext/gd/libgd/gd_jpeg.c contains:

```
const char * gdJpegGetVersionString()
{
        switch(JPEG_LIB_VERSION) {
                case 62:
                        return "6b";
                        break;

                case 70:
                        return "7";
                        break;

                case 80:
                        return "8";
                        break;

                case 90:
                        return "9 compatible";
                        break;

                default:
                        return "unknown";
        }
} 
```

Please add

```
                case 100:
                        return "10 compatible";
                        break;

```

LibJPEG 10 was released on January 25th, 2026. Its file jpeglib.h contains:

```
/* Version IDs for the JPEG library.
 * Might be useful for tests like "#if JPEG_LIB_VERSION >= 100".
 */

#define JPEG_LIB_VERSION        100     /* Compatibility version 10.0 */
#define JPEG_LIB_VERSION_MAJOR  10
#define JPEG_LIB_VERSION_MINOR  0

```

Thanks a lot.

### PHP Version

```plain
8.5.4
```

### Operating System

Any