TTG for IPBind wrong extension name

The standard[1] for extension naming is to use the XC prefix for the internal extension points, rather than for a new constructor.

This is violated for IPBind, having

data IPBind id
  = IPBind
        (XIPBind id)
        (Either (Located HsIPName) (IdP id))
        (LHsExpr id)
  | XCIPBind (XXIPBind id)

Swap the usage of XIPBind and XCIPBind

[1] https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow#Namingconventions

Trac metadata

Trac field	Value
Version	8.4.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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