Remove INLINEs from GBinary/GSum methods

These interact very badly with GHC 7.9.x's simplifier

See also

 - https://ghc.haskell.org/trac/ghc/ticket/9630 and

 - https://ghc.haskell.org/trac/ghc/ticket/9583

Submitted upstream as https://github.com/kolmodin/binary/pull/62