Fix XP3 creation with RiddleCxCrypt

[CBerJun]

Issue

The current XP3 RiddleCxCrypt encryption is broken.

To reproduce, just create any XP3 pack that uses RiddleCxCrypt ("Riddle Joker" or "Café Stella to Shinigami no Chou"). Then you decrypt it and see that the file extracted is not the same as the original file.

For example, I created a pack with one file test.txt containing the following bytes:

30 31 32 33 34 35 36 37 38 39 41 42 43 44 45 46

Creating a XP3 with "Café Stella to Shinigami no Chou" crypt and then extracting it, the extracted test.txt has the following bytes:

83 a6 b6 8a 33 1b 35 9a 38 39 41 42 43 44 45 46

Cause

Look at GameRes.Formats.KiriKiri.RiddleCxCrypt.Encrypt:

GARbro/ArcFormats/KiriKiri/YuzCrypt.cs

Lines 137 to 141 in 71a9382

	public override void Encrypt (Xp3Entry entry, long offset, byte[] buffer, int pos, int count)
	{
	base.Encrypt (entry, offset, buffer, pos, count);
	ProcessFirstBytes (entry, offset, buffer, pos, count);
	}

base.Encrypt would call GameRes.Formats.KiriKiri.CxEncryption.Encrypt:

GARbro/ArcFormats/KiriKiri/KiriKiriCx.cs

Lines 205 to 208 in 71a9382

	public override void Encrypt (Xp3Entry entry, long offset, byte[] values, int pos, int count)
	{
	Decrypt (entry, offset, values, pos, count);
	}

which would call Decrypt again as the algorithm is symmetric, but Decrypt is virtual and this would call GameRes.Formats.KiriKiri.RiddleCxCrypt.Decrypt:

GARbro/ArcFormats/KiriKiri/YuzCrypt.cs

Lines 131 to 135 in 71a9382

	public override void Decrypt (Xp3Entry entry, long offset, byte[] buffer, int pos, int count)
	{
	ProcessFirstBytes (entry, offset, buffer, pos, count);
	base.Decrypt (entry, offset, buffer, pos, count);
	}

As you can tell from the process, ProcessFirstBytes gets invoked twice (once before the Cx crypt and once after) when it should have only been invoked once after the Cx crypt.

Fix

Let CxEncryption.Encrypt call CxEncryption's own implementation of Decrypt only. This fix should not break other crypts derived from CxEncryption as they don't call base.Encrypt or rely on the fact that base.Encrypt calls their Decrypt.

[crskycode]

Thank you