astro/merkaartor: switch to using WebEngine

- it's not quite clear, whether an engine is still required.

Qt5Webkit will be removed at the end of the year.

See: commit e8e65e7

    www/qt5-webkit: mark for deletion

    Qt upstream switched to QtWebEngine quite a while ago, and the maintenance
    of QtWebKit was carried out by a separate person.
    Unfortunately, no release or updates have been pushed in the recent
    years.

    Note: there is a fork [1] of the used fork [2], that might be viable for people that
    really still need to rely on Qt5Webkit.

    [1] https://github.com/movableink/webkit/
    [2] https://github.com/qtwebkit/qtwebkit

astro/merkaartor/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	merkaartor
 PORTVERSION=	0.19.0
-PORTREVISION=	15
+PORTREVISION=	16
 CATEGORIES=	astro
 
 MAINTAINER=	dev2@heesakkers.info
@@ -22,7 +22,7 @@ USE_LDCONFIG=	yes
 QMAKE_ARGS=	SYSTEM_QUAZIP=1
 USE_QT=		buildtools:build \
 		concurrent core gui imageformats network printsupport svg \
-		webkit widgets xml
+		webengine widgets xml
 
 OPTIONS_DEFINE=	DEBUG GEOIMAGE NLS PROTOBUF ZBAR
 OPTIONS_DEFAULT=	GEOIMAGE