This updates simdutf to my fork which has a SIMDUTF_NO_LIBCXX option
that removes all libc++ and libc++ ABI dependencies.
From there, the hand-written simd code we have has been updated to also
no longer use any libc++ features. Part of this required removing utfcpp
since it depended on libc++ (`<iterator>`).
libghostty-vt now only depends on libc.
Standalone projects demonstrating the Ghostty library APIs.
The directories starting with c- use the C API and the directories
starting with zig- use the Zig API.
Every example can be built and run using zig build and zig build run
from within the respective example directory.
Even the C API examples use the Zig build system (not the language) to
build the project.
e51de8b58f