Some ineffective INLINE pragmas on recursive definitions in bytestring.

Compiling GHC with lint revealed some ineffective INLINE pragmas in bytestring.

In particular in Data/ByteString/Lazy.hs:

* compareLength
* packZipWith
* foldr'

For foldr' it probably doesn't matter.

But for packZipWith and compareLength splitting the recursive part of the function into a local recursive definition would allow the non-recursive part to inline and allow those functions to optimize better when applied to statically known empty chunks.

NB: They are ineffective as GHC will never inline self-recursive functions.

Start in Data/ByteString/Lazy.hs with compareLength, packZipWith, and foldr'. Review how their recursive definitions interact with the INLINE pragmas and GHC's treatment of self-recursive functions. Done means the ineffective pragmas are addressed and the non-recursive portions of compareLength and packZipWith can optimize for statically known empty chunks.

Written by the indexing model from the issue text.