write TODO comments for implementation notes

src/string.c

@@ -1,10 +1,22 @@
 #include "string.h"
 
-int   memcmp(const void *s1, const void *s2, usize n) {
+int memcmp(const void *s1, const void *s2, usize n)
+{
+	/* TODO: Compare n bytes of s1 with s2, performing *s1-*s2.
+	 * Returning if non-zero or out of bounds. */
 }
 
-void *memset(void *s, int c, usize n) { }
+void *memset(void *s, int c, usize n)
+{
+	/* TODO: Fill memory with c */
+}
 
-void *memcpy(void *restrict dst, const void *restrict src, usize n) { }
+void *memcpy(void *restrict dst, const void *restrict src, usize n)
+{
+	/* TODO: Copies memory area, not allowing overlap */
+}
 
-void *memmove(void *dst, const void *src, usize n) { }
+void *memmove(void *dst, const void *src, usize n)
+{
+	/* TODO: Moves memory area, allowing overlap */
+}