[geary] Add tooltips to composer spellcheck popover.

[Michael Gratton <mjog src gnome org>]

commit 2c00fe9a48ea63e177b7f0e59867f31d83f04db6
Author: Michael James Gratton <mike vee net>
Date:   Sun Feb 5 13:31:45 2017 +1100

    Add tooltips to composer spellcheck popover.

 src/client/composer/spell-check-popover.vala |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/client/composer/spell-check-popover.vala b/src/client/composer/spell-check-popover.vala
index c16b896..0cc5221 100644
--- a/src/client/composer/spell-check-popover.vala
+++ b/src/client/composer/spell-check-popover.vala
@@ -114,9 +114,11 @@ public class SpellCheckPopover {
 
             if (is_lang_visible) {
                 remove_button.set_image(new Gtk.Image.from_icon_name("list-remove-symbolic", sz));
+                remove_button.set_tooltip_text(_("Remove this language from the preferred list"));
             }
             else {
                 remove_button.set_image(new Gtk.Image.from_icon_name("list-add-symbolic", sz));
+                remove_button.set_tooltip_text(_("Add this language to the preferred list"));
             }
         }