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)