gitignore: stop tracking all generated build outputs
Untrack and ignore all autotools-generated files (Makefile.in, configure,
config.h.in, compile, config.guess, config.sub, depcomp, install-sh,
missing, ltmain.sh, m4/libtool.m4, INSTALL), generated Makefiles,
compiled binaries, object files, libtool artifacts, generated headers,
man pages, and Wayland protocol headers.
Run `autoreconf -i && ./configure` to regenerate before building.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>