The "deactivate" handler for EAttachmentButton's popup menu was never
disconnected, and I suspect it may be getting invoked after the button
has been finalized.
Rewrite the attachment UI to better utilize GIO and also to migrate from
GnomeIconList to GtkIconView. This also introduces a "List View" option
similar to Nautilus, as well as the EAttachmentHandler framework for
extending attachment handling (may eventually replace EMFormatHook).
This commit also fixes a number of secondary attachment bugs:
Bug 311609 – new attachment bar should use regular gtk+ expander
Bug 314923 – Drag and Drop in attachment window is inconsistent and
requires additional click
Bug 338179 – attachment saving ...
Bug 350364 – Action to get info about attachments
Bug 383047 – Viewing mail attachments
Bug 427235 – Can't copy attachment mime type string
Bug 454091 – Cannot save multiple attachments who have the same name
Bug 494629 – Rethink composer's attachment UI
Bug 553970 – Evolution ignores umask when saving attachments
Bug 577375 – mailto: and attach doesn't URL un-escape