[meson] add meson options to disable man pages

The smi man pages are not needed for every type of distribution and instead of disabling them by hacks (https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/addons/addon-depends/chrome-depends/shared-mime-info/patches/no-man-no-html.patch) it would ne nice if we could just disable them by build opts.