Fix warnings for deprecated import behavior.

[rcorre]

The language is cracking down on leaking imports, leading to the following deprecation messages:

allegro5/file.d(100,6): Deprecation: allegro5.utf8.va_list is not
visible from module file

allegro5/blender.d-mixin-38(40,22): Deprecation: module
allegro5.color_ret is not accessible here, perhaps add 'static import
allegro5.color_ret;'

This fixes both of the above.

[SiegeLord]

Thanks!