Bug#906646: Acknowledgement (RFS: double-conversion/3.0.0+git20180802.4e8b3b5-1 [ITA, tensorflow deps])

[Lumin]

Hi mentors,

I've tested building all double-conversion's reverse dependencies including
libqt5core5a in unstable, none of them was broken.

Test platform is ppc64el instead of amd64.