Update changelog for 5.2.1

Change-Id: Ieca0a1ed696a81019c8a0d223c6511b3ed6f0201
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Doc: Fix typo

Change-Id: I4975f634da1b02e90e84f704583e5cabdf277e5a
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: Icbc8dda64ebc3591a1cf8751ce513ab843d5233f
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I5eed3f81fe220f82d1eba27d7e7a62803fea5e49