[klibc] include: [stdio.h] Add getc_unlocked

module-init-tools uses it.
Trivial as klibc has no threading.

Signed-off-by: maximilian attems <max@stro.at>
diff --git a/usr/include/stdio.h b/usr/include/stdio.h
index 69d80b3..7d3dca6 100644
--- a/usr/include/stdio.h
+++ b/usr/include/stdio.h
@@ -78,6 +78,8 @@
 __extern int fgetc(FILE *);
 __extern char *fgets(char *, int, FILE *);
 #define getc(f) fgetc(f)
+__extern int getc_unlocked(FILE *);
+#define getc_unlocked(f) fgetc(f)
 #define getchar() fgetc(stdin)
 __extern int ungetc(int, FILE *);