[SDK] Minor improvements to CRT, RTL, and headers

Signed-off-by: Quinn Stephens <quinn@osmora.org>

SDK/CRT/STRING/mem.c

@@ -64,21 +64,17 @@ memmove (
 
     /* Check for overlap */
     if (src > dest || ((char *)src + count) < (char *)dest) {
-        /* Low-to-high copy, like memcpy() */
-        while (count--) {
-            *(char *)dest = *(char *)src;
-            dest = (char *)dest + 1;
-            src = (char *)src + 1;
-        }
-    } else {
-        /* High-to-low copy */
-        dest = (char *)dest + count - 1;
-        src = (char *)src + count - 1;
-        while (count--) {
-            *(char *)dest = *(char *)src;
-            dest = (char *)dest - 1;
-            src = (char *)src - 1;
-        }
+        /* Low-to-high copy, use memcpy() */
+        return memcpy(dest, src, count);
+    }
+
+    /* High-to-low copy */
+    dest = (char *)dest + count - 1;
+    src = (char *)src + count - 1;
+    while (count--) {
+        *(char *)dest = *(char *)src;
+        dest = (char *)dest - 1;
+        src = (char *)src - 1;
     }
 
     return ptr;