Restore legacy Connection slots. Restore compilation on Qt 5.12.

app/qml/BurnInEffect.qml

@@ -76,7 +76,7 @@ Loader {
             Connections {
                 target: kterminal
 
-                function onImagePainted() {
+                onImagePainted: {
                     completelyUpdate()
                 }
             }
@@ -84,19 +84,19 @@ Loader {
             Connections {
                 target: appSettings
 
-                function onBurnInChanged() {
+                onBurnInChanged: {
                     burnInEffect.restartBlurSource()
                 }
 
-                function onTerminalFontChanged() {
+                onTerminalFontChanged: {
                     burnInEffect.restartBlurSource()
                 }
 
-                function onRasterizationChanged() {
+                onRasterizationChanged: {
                     burnInEffect.restartBlurSource()
                 }
 
-                function onBurnInQualityChanged() {
+                onBurnInQualityChanged: {
                     burnInEffect.restartBlurSource()
                 }
             }

app/qml/PreprocessedTerminal.qml

@@ -47,14 +47,14 @@ Item{
     Connections {
         target: copyAction
 
-        function onTriggered() {
+        onTriggered: {
             kterminal.copyClipboard()
         }
     }
     Connections {
         target: pasteAction
 
-        function onTriggered() {
+        onTriggered: {
             kterminal.pasteClipboard()
         }
     }
@@ -63,29 +63,29 @@ Item{
     Connections {
         target: appSettings
 
-        function onFontScalingChanged() {
+        onFontScalingChanged: {
             terminalContainer.updateSources()
         }
 
-        function onFontWidthChanged() {
+        onFontWidthChanged: {
             terminalContainer.updateSources()
         }
     }
     Connections {
         target: terminalContainer
 
-        function onWidthChanged() {
+        onWidthChanged: {
             terminalContainer.updateSources()
         }
 
-        function onHeightChanged() {
+        onHeightChanged: {
             terminalContainer.updateSources()
         }
     }
     Connections {
         target: terminalWindow
 
-        function onActiveChanged() {
+        onActiveChanged: {
             kterminal.forceActiveFocus()
         }
     }

app/qml/SettingsTerminalTab.qml

@@ -69,7 +69,7 @@ ColumnLayout {
                 Connections {
                     target: appSettings
 
-                    function onTerminalFontChanged() {
+                    onTerminalFontChanged: {
                         fontChanger.updateIndex()
                     }
                 }