Resolves#410. notcurses_at_yx() accepted a cell*, but the
gcluster of this cell was always set to 0. The EGC is instead
a heap-allocated copy, returned as the primary return value.
This is due to the absence of an egcpool to bind against.
Existing callers can be converted thus:
* instead of passing cell 'c', pass &(c)->attrword, &(c)->channels
* either initialize 'c' with CELL_TRIVIAL_INITIALIZER, or set its
gcluster field to 0 following the call
I've updated all calls from tests/demos, updated the docs, and
updated the C++ and Python wrappers.
* CMake: add USE_PANDOC, USE_DOXYGEN options #101
* README: mention rust
* start integrating rust into build #101
* CMake: add USE_NETWORK option for cargo
* Debian: build-dep on doxygen
* rust: colloquy checks in Cargo.lock
* extract NCKEY defines into their own include
* colloquy: use clap to parse CLI args
* CMake: unify option namespace
* Python: update include path
* Rust: fix up --frozen workings for -DUSE_NETWORK=off
* CMake: abstract out colloquy a little
* Sync direct.hh to the New Way
* palette_set: update pal256 damage map #230
* drone: use newest builders
* palette: send oc on exit for color reset #285
* palette_new: copy existing palette in #230
* Python: use checkRGB everywhere
* more palette unit testing
* add ncplane_set_*_palindex()
* render fg palindex #230
* palette index color is out of 1000
* jungle demo works #253
