Add Toolchain page and bring the wiki up to v6.4.9
Document the in-OS C toolchain on a new Toolchain page: the userland libc,
the cc shell builtin, the TinyCC 0.9.27 port, and the tcc-compiles-tcc
self-host milestone (the in-OS tcc compiling its own ~40k-line source to a
valid x86-64 object).
Refresh the surrounding pages to match: Version-History through v6.4.9,
plus cross-links and content updates across the source-tree, userspace,
shell, filesystem, security and reference pages.
Wiki: Version History to v5.9.180 (add v5.9.113-180) + bump current-version markers
Adds the 68 releases v5.9.113 to v5.9.180 to Version-History: v5.9.113-126 extend the general-maintenance era, and a new 'Desktop image viewing and Selene's CSS engine' era covers v5.9.127-180. Bumps the current-release marker to v5.9.180 across Home, Index, Version-History, the footer, the Architecture KERNEL_VERSION row, Command-Reference, the FAQ release count (now 342), and the HOWTO free-syscall note. Source-Tree-Reference keeps its explicit v5.9.112 line-count snapshot (per-file counts were not recomputed).
Wiki update — v5.9.112, maintenance pass, new reference pages, source-tree reorg, full version history up to latest release
Wiki update - v5.9.88 animated GIFs, new HOWTO guides, glossary, FAQ, debugging, contributing
New pages: Contributing, Debugging, FAQ, Glossary, HOWTO-Add-a-GUI-application,
HOWTO-Add-a-shell-command, HOWTO-Add-a-system-call, HOWTO-Write-a-userspace-program,
Kernel-Data-Structures, Troubleshooting, Wiki-Conventions.
All existing pages updated through v5.9.88 (animated GIF playback, image decoders).