Check for ICU at configure time the same way we add it later

Use pkg-config to get the right ICU library when searching for it at
config time. This matches how it is build with later.

Task-number: QTBUG-41750
Change-Id: I134ecdeb523eab225ef66f4dcc14ae4e25ea4eca
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Get rid of old harmattan workaround hurting Qt on ARM

Change-Id: Ieecee7c05e78117e8c9fc335f60970e2144ede81
Reviewed-by: Michael Bruning <michael.bruning@digia.com>