Automatically rotate image based on accelerometer values

Device orientation is provided by net.hadess.SensorProxy
iio-proxy-service. If there is no accelerometer on target platform,
then window orientation from X11/wayland is used as before.

meson.build

@@ -54,6 +54,7 @@ executable('megapixels',
   'src/matrix.c',
   'src/pipeline.c',
   'src/process_pipeline.c',
+  'src/rotation.c',
   'src/zbar_pipeline.c',
   'src/dcp.c',
   resources,
@@ -126,6 +127,8 @@ if clang_format.found()
     'src/pipeline.h',
     'src/process_pipeline.c',
     'src/process_pipeline.h',
+    'src/rotation.c',
+    'src/rotation.h',
     'src/zbar_pipeline.c',
     'src/zbar_pipeline.h',
     'tools/camera_test.c',