Some more improvement of selection specifier parsing. NSRangeSpecifier seems to have a bug when determining its indices, so we do some of it ourselves. Also specifiers that specify several disconnected ranges (e.g. a whose specifier). Add some comments. 
Some more improvement of selection specifier parsing. NSRangeSpecifier seems to have a bug when determining its indices, so we do some of it ourselves. Also specifiers that specify several disconnected ranges (e.g. a whose specifier). Add some comments. 

git-svn-id: 765db44a9620ed55f4f8addfd3c14fe8cd57f6bb@2276 0fceea05-a30d-0410-8a8b-80ef821fb0a1

nanoant/Skim,nanoant/Skim,nanoant/Skim,nanoant/Skim,nanoant/Skim