Suggest similar names in imports

This commit adds similar name suggestions when importing. For example

  module A where { spelling = 'o' }
  module B where { import B ( speling ) }

will give rise to the error message:

  Module ‘A’ does not export ‘speling’.
  Suggested fix: Perhaps use ‘spelling’

This also provides hints when users try to import record fields defined
with NoFieldSelectors.