input/wav: add channel list checks for file re-read

input/wav: add channel list checks for file re-read

Do for the WAV input module what commit 08f8421a9e82 did for VCD. Check
the channel list for consistency across re-imports of the same file.
This addresses the WAV part of bug #1241.

This commit also changes the WAV module's reset() method's behaviour.
The previous implementation only created channels once, and re-used that
channel list when the file got re-read. Which could cause issues when
the file's properties changed between re-runs. This implementation
always creates the channel list upon every file import, and ensures a
consistent channel list across re-imports. This follows the approach
that was taken in all other input modules before.