Make suppress macro export variable in outer scope automatically

[Tortar]

Actually this fixes everything, so no need for the suggested workaround in #67, now:

julia> using Suppressor

julia> @suppress g = 1

julia> module M
           using Suppressor
           @suppress g = 1
       end
Main.M

julia> g
1

julia> Main.M.g
1

It should probably applied to all macros actually, but I'd like to know what mantainers think of this

[Tortar]

this is breaking though