change the version format for development builds

The suffix is now "-dev-COMMITHASH" which makes it easier for users to
differentiate between final releases and interim development snapshots.
update to the latest Qt to fix multiple issues

fixes #1539 via wkhtmltopdf/qt@5a8d870c018db33ee63dad821a260939e1b2fbd0
fixes #1638 via wkhtmltopdf/qt@b18df9fc8cd717e43cab87f7b295c4cb2fc39704
fixes #1722 via wkhtmltopdf/qt@7683bbb8c60f595d44692e34f79e3e359580b3bf

also sync the changelog with latest changes