v2.3.9

• Fixed major regressions from 2.3.8: menu highlighting is working once more, as are pointer inputs (mice) and the 8x1 plotter. Sorry about that!
• notcurses_detected_terminal() and ncdirect_detected_terminal() now both return a heap-allocated string, which will contain the terminal version if Notcurses was able to detect it. This result ought be free()d.
• Added ncplane_moverel() thanks to @tomek-szczesny.
• Documented ncplane_move_yx() in notcurses_plane.3, and removed the false comment that "passing -1 as a coordinate will hold that axis constant" from USGAE.md and notcurses.h. This has never been true.
• Added ncdirect_putegc() to perform Unicode segmentation. It returns the number of columns consumed, and makes available the number of bytes used by the EGC.
• ncmenus can now be used with any plane, not just the standard plane.
• Added ncchannels_reverse(), which reverses the color aspects of the two channels, while keeping other elements constant.
• CHANNELS_RGB_INITIALIZER and CHANNEL_RGB_INITIALIZER have been renamed NCCHANNELS_INITIALIZER and NCCHANNEL_INITIALIZER. The former two are now deprecated, and will be removed for ABI3.