Moved libultra files to /lib/ directory

lib/src/string.c

@@ -0,0 +1,34 @@
+/* The comment below is needed for this file to be picked up by generate_ld */
+/* RAM_POS: 0x800CE170 */
+
+#include "types.h"
+#include "macros.h"
+
+void *memcpy(void *dst, const void *src, size_t size) {
+    u8 *_dst = dst;
+    const u8 *_src = src;
+    while (size > 0) {
+        *_dst++ = *_src++;
+        size--;
+    }
+    return dst;
+}
+
+size_t strlen(const char *str) {
+    const u8 *ptr = (const u8 *) str;
+    while (*ptr) {
+        ptr++;
+    }
+    return (const char *) ptr - str;
+}
+
+char *strchr(const char *str, s32 ch) {
+    u8 c = ch;
+    while (*(u8 *)str != c) {
+        if (*(u8 *)str == 0) {
+            return NULL;
+        }
+        str++;
+    }
+    return (char *) str;
+}