Build failure from r951037

    [javac] D:\POI Build\src\java\org\apache\poi\poifs\crypt\Decryptor.java:107: cannot find symbol
    [javac] symbol  : method copyOf(byte[],int)
    [javac] location: class java.util.Arrays
    [javac] return Arrays.copyOf(x3, requiredKeyLength);
    [javac] ^
    [javac] D:\POI Build\src\java\org\apache\poi\poifs\crypt\Decryptor.java:120: cannot find symbol
    [javac] symbol  : method copyOf(byte[],int)
    [javac] location: class java.util.Arrays
    [javac] byte[] verifierHash = Arrays.copyOf(cipher.doFinal(info.getVerifier().getVerifierHash()), calcVerifierHash.length);
    [javac] ^
    [javac] 2 errors

This .copyOf() method was added in 6, so we have to remove it to stay 5.x compliant.