Stringify plugin functions in util.deepHash.
Stringify plugin functions in util.deepHash.

This isn't perfect, but it's better than just ignoring plugin functions
and risking hash collisions between compilations that use totally
different plugins and presets.

Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor,Hansoft/meteor