- Remove `HAVE_LCMS` definition in favor of `HAVE_LCMS2`.
- Remove `HAVE_WINDOWS_H` definition in favor of `G_OS_WIN32`.
- Remove stray `vips_text_get_type` in `conversion.c`.
- Remove duplicated `unistd.h` include.
- Remove redundant `strcasecmp` definition, we use `g_ascii_strcasecmp` everywhere.
- Remove unnecessary header checks in `configure.ac` and `meson.build`.
- Ensure `unistd.h` include is guarded with `HAVE_UNISTD_H`.
- Fail early when `-Dfontconfig=enabled` and `pangoft2` is not found.