boost parameters and gcc -Wunused-parameter

[plasmahh@…]

Hi, the BOOST_PARAMETER_FUNCTION macro leaves a helper function with the parameter boost_parameter_enabler_argument around. however, that parameter is never used, so gcc with -Wunused-parameters leads to really ugly template infested warnings that the user has no control over. I suggest therefore either to remove the name of the parameter entirely (or rather comment it out for documentation purposes), or if this is not supported by all compilers (gcc 4.2-4.4 do work here) to have this parameter casted to void in the function body.

[Daniel Wallin]

(In [53402]) Silence "unused parameter" warning in BOOST_PARAMETER_FUNCTION(). Fixes #2808.