Update double-conversion to version 3.2.1 / rev 13 via SR 998147
https://build.opensuse.org/request/show/998147
by user pgajdos + dimstar_suse
- update to 3.2.1
* Disable quiet nan test on windows
* Test on all platforms.
* Fix warnings on Windows
* Run ctests first.
* Give shared-lib option and test install
* Install Windows debbuger (pdb) files.
* Add a cast to silence a signedness conversion warning.
* Issue #184 : Fixed all -Wzero-as-null-pointer-constant warnings (forwarded request 997609 from dirkmueller)