test: loaders: Fix whitespaces.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
tests: loaders: New SaveLoad test.

The test calls for each format and each pixel corresponding save
function. The expected behavior is either failure with ENOSYS or
success. In case of success the image is loaded back and checked.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: TIFF: Handle correctly on unsuppored pixeltypes.

Make the saver exit with ENOSYS on unsupported pixeltypes.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: LineConvert: Add more conversions.

Add match for identity (returns NULL convert functions).

Add conversions between xRGB888 and RGB888 and BGR888.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: PNM: Make use of LineConvert.

So far only for PNM and PPM.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: PNM: Fix SavePBM.

Inverse the value on SavePBM.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
tests: loaders: Add simple pixelcheck to save_load.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: BMP, JPG: Simplify LineConvert usage.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>