Fix new instances or changes in gcc flagged unused code. These are
mostly related to variables which are not used when debugging is
disabled and the ASSERTs are compiled out.
within an ASSERT with the ASSERTV macro which will ensure it will
be removed when the ASSERTs are commented out. This makes gcc much
happier, makes the variables usage explicit, and removes the need
for the compiler to detect it is unused and do the right thing.
compile option. In most case the variables are only unused when
debugging is disabled (ASSERT) however they do waste stack if that
case if the compiler doesn't optimize it out (it should). But more
importantly disabling this warning prevent us from noticing legit
unused variables accidentally left in other place of the code.
Brian Behlendorf