error-box: Wrap the secondary error label to deal with long messages
base-item: Style fixes
base-item: Serialize thumbnail creation for all items

We don't want to spawn 50 different threads to create the thumbnails
of all the items in the first batch. Instead, we want to create them
one at a time. Hence, use a class level lock instead of a per-object
one.
properties-dialog: Fix a compiler warning
build: Wrap glib-mkenums with $(AM_V_GEN)
main-window: Do not hide the headerbar when maximized
Updated Czech translation
Updated Galician translations
Prepare 3.9.90
Updated Polish translation
dlna: Use G_STMT_START/G_STMT_END/G_STRFUNC

https://bugzilla.gnome.org/show_bug.cgi?id=706513
Rename all singleton public constructors to _dup_singleton()

Using _dup_singleton() instead of _new() makes more clear that we're not
really allocating a new object, but just taking a reference to an
already existing one.

https://bugzilla.gnome.org/show_bug.cgi?id=703280
dlna-renderers-manager: Style fixes
Unicode!
Updated Brazilian Portuguese translation
Updated slovak translation
Updated Hungarian translation
Updated slovak translation
Updated Slovenian translation
Tajik translation added