More InspIRCd numeric updates.

[SadieCat]

• RPL_SYNTAX is a usage of RPL_TEXT in 2.0 not a collision.
• Add a bunch of numerics added in the InspIRCd 3.0 dev branch.
• Add notes that some InspIRCd numerics have been replaced/moved.

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I have not marked the replaced/moved numerics as deprecated yet because 3.0 is still an alpha and won't be out for quite a while.

[DanielOaks]

Nice, thanks