- fix build without pandoc on 32bit x86 and arm

- Update to version 2.1.5
* Notcurses now depends on GNU Readline at build and runtime,
entirely for the benefit of direct mode, which now prepares
GNU Readline for safe use (unless the new
NCDIRECT_OPTIONS_NO_READLINE is used). ncplane_putstr_yx(),
ncplane_putstr_stained(), and ncplane_putnstr_yx() now return
the number of columns output, as long documented (they were
mistakenly returning the number of bytes).
* cplane_abs_yx() has been added, returning the absolute
coordinates of the plane's origin (i.e. coordinates relative
to its pile).
- Update to version 2.1.4
* Direct mode now supports NCDIRECT_OPTION_NO_QUIT_SIGHANDLERS,
and by default installs signal handlers similar to those of
fullscreen mode. They will attempt to reset the terminal, and
propagate the signal.
* Add channels_fg_palindex() and channels_bg_palindex().
- Update to version 2.1.3
* ncdirect_styles_{set, on, off}() have been deprecated in favor
of ncdirect_{set, on, off}_styles(), to match ncplane_
equivalents.
* ncdirect_raster_frame() no longer requires blitter nor scale.
* ncdirect_{fg, bg}_{default, rgb}() have been deprecated in
favor of ncdirect_set_{fg, bg}_{default, rgb}(), to match
ncplane.
- Update to version 2.1.2
* Add notcurses_linesigs_enable() and notcurses_linesigs_disable().
* Divide ncdirect_render_image() into component