This adds the `Half Float Precision` option in the image property panel. This option is only available on float textures and is enabled by default. Adding a flag inside the imbuf (IB_halffloat) on load is done for EXR and PSD formats that can store half floating point (16bits/channels). The option is then not displayed in this case and forced. Related task T73086 Reviewed By: brecht Differential Revision: https://developer.blender.org/D6891