thumbnailer: Unbreak thumbnailing of GIFs

See merge request !32

The GIF codec throws GDK_PIXBUF_ERROR_INCOMPLETE_ANIMATION if it's
closed without decoding all the frames. The thumbnailer has always,
both now with gdk_pixbuf_new_from_file_at_scale and earlier, decoded
only the first animation frame, which is why this specific error needs
to be ignored [1].

Fixes: dd1f222f

[1] gnome-desktop@f9b2c480

#99

ci: add a msys2 mingw64 job

See merge request !29

When building without GDK_PIXBUF_USE_GIO_MIME detect the format based on the
fill extension and not the mime type.

This makes these tests pass on Windows.

When cloning the repo with git on Windows the symlinks end up being
normal files which contain the target path as text.

Make this kinda work by detecting if the files contain ascii only
and then treating the content as a filename in the parent directory.

So we use the right path encoding on Windows and don't interpret the content
as text.

This makes the pixbuf-threads run on Windows.

gif: Remove unused variable

See merge request !30

Add pkgconfig variables for binary utilities

Closes #89

See merge request !12

Cross compile building

Closes #64

See merge request !20

gif: Fix debug printf format warnings

See merge request !24

meson: use an autotools compatible compatibility_version/current_version on macOS

See merge request !23

Use the same versioning scheme as libtool did with the autotools build.
Otherwise switching gdk-pixbuf from meson to autotools makes all libraries
linking to it fail since the version is too low.

This ensures that the enums are generated before compiling the headers.

Fixes variations on this error for different loaders

pixbuf@@staticpixbufloader-qtif@sta/io-qtif.c.o' -c ../gdk-pixbuf/io-qtif.c
In file included from ../gdk-pixbuf/io-qtif.c:34:0:
../gdk-pixbuf/gdk-pixbuf.h:40:46: fatal error: gdk-pixbuf/gdk-pixbuf-enum-types.h: No such file or directory

Some linux-like platforms (e.g. Android) don't have a mime-info database
readily available for use.

Workaround to install modules with .so suffix on osx

See merge request !19

queryloaders: add missing include for OSX when using relocations

See merge request !18

The old autotools build system was create .so files instead of dylib
and G_MODULE_SUFFIX does not take into account dylib suffixes so
we should at least for now use .so until we have a better api to
use than the one provided by gmodule.