meson: Change build options

Following the new meson porting guidelines, this patch renames the
build options as follows:

- Remove the 'enable' prefix from boolean options.
- The character separator in multi-word options has been changed
  to underscore.

The `debug` and `strict-cc` options have also been removed because
they can be enabled by using meson's options.

https://bugzilla.gnome.org/show_bug.cgi?id=791421