make this variable static.
make this variable static.

This is the nasty bug with mixer module... it didn't happen before 
because I always compile with -fvisibility=hidden




SVN revision: 44992

tasn/enlightenment,FlorentRevest/Enlightenment,rvandegrift/e,tasn/enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment,rvandegrift/e,tizenorg/platform.upstream.enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment