Remove warning in src/lib/printk.c

[webconn]

**_/antares/src/lib/printk.c:17:15: warning: ‘p_stdin’ defined but not used [-Wunused-variable]
static FILE *_p_stdin = &g_early_stdin;

Let's do something with this.

[nekromant]

Well, there should be a wrapper for scank() as well there, but I didn't have time to add it.