move gcc required functions to string.c

src/kernel/memory.c

@@ -210,12 +210,4 @@ void heap_stats() {
     kprint("Free: "); kprint_hex(free_size); kprint(" bytes in "); kprint_int(free_blocks); kprint(" blocks\n");
     kprint("Total metadata overhead: "); kprint_int((used_blocks + free_blocks) * sizeof(HeapHeader)); kprint(" bytes\n");
     kprint("-------------------------\n");
-}
-
-void *memset(void *s, int c, size_t n) {
-    unsigned char *p = s;
-    while (n--) {
-        *p++ = (unsigned char)c;
-    }
-    return s;
 }

src/lib/string.c

@@ -0,0 +1,10 @@
+#include <stddef.h>
+#include "string.h"
+
+void *memset(void *s, int c, size_t n) {
+    unsigned char *p = s;
+    while (n--) {
+        *p++ = (unsigned char)c;
+    }
+    return s;
+}

src/lib/string.h

@@ -0,0 +1,6 @@
+#ifndef STRING_H
+#define STRING_H
+
+void *memset(void *s, int c, size_t n);
+
+#endif