Tweak to spectral selection behavior when one edge is tied.

Idea by Martin.  Implemtation by Paul Licameli.

git-svn-id: http://audacity.googlecode.com/svn/audacity-src/trunk@13592 47890b92-0858-11df-a26f-8b716316a5bc
Fixed warnings about AUDACITY_DLL_API.

If one class is exported, then all the classes it derives from must be exported too, otherwise we get warnings wherever it is used.

git-svn-id: http://audacity.googlecode.com/svn/audacity-src/trunk@13593 47890b92-0858-11df-a26f-8b716316a5bc