Fix GCC error

In case we don't have a recent enough poppler, return the enum value
instead of zero, or GCC will complain about immplcitly casting an int to
an enum.

https://bugzilla.gnome.org/show_bug.cgi?id=677867
Updated Norwegian bokmål translation
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Assamese translation reviewed
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document: Fix crash on ev_document_add_filters.

See https://bugzilla.gnome.org/show_bug.cgi?id=678563.
Fix proposed by Christian Persch.
build: Require glib 2.32
libdocument: Remove glib < 2.32 compat code
libview: Remove glib < 2.32 compat code
previewer: Remove glib < 2.32 compat code
shell: Remove glib < 2.32 compat code
dvi: Remove glib < 2.32 compat code
thumbnailer: Remove glib < 2.32 compat code
build: Add configure check for glib-compile-resources
previewer: Use GResource for data files
toolbar-editor: Add methods to load from GResource
shell: Use GResource for data files
thumbnailer: Remove unused code

The code to overlay an icon is unused since commit 808285c968d09e3be2a159cd304346c180763d54.