Expose suggestions scores

[kevina]

This adds the following methods/functions:

AspellSuggestions * aspell_speller_suggestions(AspellSpeller *, const char * word, int word_size, void * unusued);

const char * * aspell_suggestions_words(AspellSuggestions *, unsigned int * len);

/* Returns the normalized scores.  The values are between 0 and 1 inclusive
 * where higher numbers indicate a better match.  The exact values may not
 * be stable between releases.  The score is currently 1/(d+1) where d is
 * the distance as given 'distances' method, however this may change in
 * future released.  This number may also incorporate other information,
 * such as the frequency, in future released. */
double * aspell_suggestions_normalized_scores(AspellSuggestions *, unsigned int * len);

/* Return the distances between the words and the correct spelling.  This
 * number is closely related to the edit distance of the word where each
 * edit is around 1.0.  Values less then 0.5 represent a typo or otherwise
 * very good match.  Values less then around 1.2 represent a good match. */
double * aspell_suggestions_distances(AspellSuggestions *, unsigned int * len);

And also add the --show-scores option to show the scores with the suggestion in aspell pipe mode.

Replaces #524.