Add missing Device.h include into GParted_Core and Win_GParted

The files GParted_Core.h, GParted_Core.cc and Win_GParted.cc all use the
Device type but don't include Device.h for it's definition.  Include it.
4 jobs for master in 22 minutes and 46 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #323823
centos_build

00:08:02

passed #323824
ubuntu_build

00:08:39

 
  Test
passed #323825
centos_test

00:12:05

passed #323826
ubuntu_test

00:14:06