Move plugin into "after".

This makes it more likely that the plugin is loaded after other plugins,
so it can remap existing mappings correctly.
Shift sources over.
Add helper functions for remapping existing mappings.
Correct case for q: -> qO mapping.
Add mappings for changing letter case linewise.
Only apply "Select All" menu fix for Vim 7.3 and earlier.

My fix was accepted into Vim 7.4.