- CGI script and index.html are moved from gluon-web to
  gluon-config-mode-core, the script is renamed to 'config'
- gluon-web and gluon-web-model base views and i18n files are symlinked
  into the new path
- gluon-web-theme is renamed to gluon-config-mode-theme and installs
  directly into the new path
- all gluon-web-* models, controllers and views are moved into the new
  path

Also bring back gluon-web-theme's i18n strings.

exec() is moved to gluon.util.

01d7a5d7dee2 perf: restrict libunwind dependency to archs that actually support libunwind
b345cc24892d libunwind: fix build with musl on PPC

These files are already located in /lib/gluon, no need to add it a second
time.

These files are already located in /lib/gluon, no need to add it a second
time.

gluon-config-mode-domain-select does not have any i18n files of its own.

By emitting Lua code to call translate() and pcdata(), we are more
flexible than when doing this internally in the parser. The performance
penalty should be negligible.

We need a bit less escaping this way.

Also fix all warnings.

Open with O_CLOEXEC, use fstat() instead of stat().

Our strings can be looked up verbatim.