autotools: Add a flag to enable or disable all plugins

[b4n]

This allows to change the default for whether every plugins are enabled or disabled, effectively allowing to easily select either all, or only a specific set of plugins.

To force enable all plugins:
configure --enable-all-plugins

To force enable all plugins, but disable Addons:
configure --enable-all-plugins --disable-addons

To force enable all plugins, but Addons which is checked automatically:
configure --enable-all-plugins --enable-addons=auto

To disable all plugins, but force enable Addons:
configure --disable-all-plugins --enable-addons

[codebrainz]

It's not clear (to me) from the M4 whether --enable-all-plugins=auto is accepted or the default (you mention "force" so it sounds like not). It might be useful and seems to be supported in the _GP_ARG_DISABLE_ALL part.

Other than that, I think this is a really good idea.

[codebrainz]

I think someone said this is already supported by Waf build system, but it might be useful to add all as a plugin name that can be used with --list-plugins, --enable-plugins, and --skip-plugins to make it explicit?

[b4n]

It's not clear (to me) from the M4 whether --enable-all-plugins=auto is accepted or the default (you mention "force" so it sounds like not). It might be useful and seems to be supported in the _GP_ARG_DISABLE_ALL part.

You can pass auto and it's the default, which doesn't change the current behavior. Passing auto however is pretty much useless as it has virtually no effect.

[frlan]

Shall we put this into 1.25?

[b4n]

@frlan I think we should, but I wished for some comments here from the people complaining about the missing feature. Without them, I can't really know if they appreciate this solution, or if they would rather have some other interface.

@zhekov do you have an opinion on this?

[b4n]

Added some docs