Replace manual array copy with System.arraycopy()

This approach is more efficient.

Author: goncalossilva

src/main/java/com/fasterxml/jackson/core/io/UTF32Reader.java

@@ -201,9 +201,7 @@ private boolean loadMore(int available) throws IOException {
         // Bytes that need to be moved to the beginning of buffer?
         if (available > 0) {
             if (_ptr > 0) {
-                for (int i = 0; i < available; ++i) {
-                    _buffer[i] = _buffer[_ptr+i];
-                }
+                System.arraycopy(_buffer, _ptr, _buffer, 0, available);
                 _ptr = 0;
             }
             _length = available;

src/main/java/com/fasterxml/jackson/core/sym/BytesToNameCanonicalizer.java

@@ -1049,9 +1049,7 @@ private static Name constructName(int hash, String name, int[] quads, int qlen)
         }
         // Otherwise, need to copy the incoming buffer
         int[] buf = new int[qlen];
-        for (int i = 0; i < qlen; ++i) {
-            buf[i] = quads[i];
-        }
+        System.arraycopy(quads, 0, buf, 0, qlen);
         return new NameN(name, hash, buf, qlen);
     }