dix: FreeAllAtoms() on reset

dix: FreeAllAtoms() on reset

==5712== 6 bytes in 1 blocks are still reachable in loss record 17 of 585
==5712==    at 0x4A074CD: malloc (vg_replace_malloc.c:236)
==5712==    by 0x3D1DE885B1: strndup (strndup.c:46)
==5712==    by 0x41CB71: MakeAtom (atom.c:121)
==5712==    by 0x55AE3E: XIGetKnownProperty (xiproperty.c:401)
==5712==    by 0x4251C9: AddInputDevice (devices.c:312)
==5712==    by 0x42AC0C: AllocDevicePair (devices.c:2657)
==5712==    by 0x425E6E: InitCoreDevices (devices.c:677)
==5712==    by 0x5ACA05: main (main.c:257)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>