Turn struct ProjectExplorerSettings into a class

We agreed to not use structs to avoid the class/struct mismatch
warnings in MSVC and clang.

Change-Id: Id1b2d89646d3a982c8d85b84b44a4e697102c220
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/projectexplorer/projectexplorer.h

@@ -60,9 +60,7 @@ class BuildConfiguration;
 class ProjectNode;
 class TaskHub;
 
-namespace Internal {
-struct ProjectExplorerSettings;
-}
+namespace Internal { class ProjectExplorerSettings; }
 
 struct ProjectExplorerPluginPrivate;
 

src/plugins/projectexplorer/projectexplorersettings.h

@@ -35,8 +35,9 @@
 namespace ProjectExplorer {
 namespace Internal {
 
-struct ProjectExplorerSettings
+class ProjectExplorerSettings
 {
+public:
     ProjectExplorerSettings() :
         buildBeforeDeploy(true), deployBeforeRun(true),
         saveBeforeBuild(false), showCompilerOutput(false),

src/plugins/projectexplorer/projectexplorersettingspage.h

@@ -39,7 +39,7 @@
 namespace ProjectExplorer {
 namespace Internal {
 
-struct ProjectExplorerSettings;
+class ProjectExplorerSettings;
 
 // Documentation inside.
 class ProjectExplorerSettingsWidget : public QWidget {