Log Message:
gegl: Update to 0.4.34

Changelog:
GEGL-0.4.34 2021-12-19
----------------------

Operations:
~~~~~~~~~~~

magick-load: use g_spawn_async instead of system to run the image magick
convert fallback - preventing shell expansion on non-escaped/filtered
paths in constructed commandline.

ripple: avoid a possible division by zero.

Build:
~~~~~~

Explicit dependency specification in meson for generated CL files.

ctx has been moved to be part of gegl-common.so nearer to the operations
using it avoiding polluting the GEGL library symbol table with the ctx
symbols.