Fix save file name with '.'s in it (#1773)

Using QFileInfo::baseName() discards everything after the first ., so
filenames like 1.2.3.4.png would be changed to 1.png. (See #1722).

Changing this to QFileInfo::completeBaseName() only discards the suffix,
so we have 1.2.3.4.jpg becoming 1.2.3.4.png, for example.

src/utils/screenshotsaver.cpp

@@ -142,7 +142,7 @@ QString ScreenshotSaver::ShowSaveFileDialog(QWidget* parent,
               dialog.selectedNameFilter().section('.', -1);
             selectedExtension.remove(QChar(')'));
             file_name =
-              info.path() + QLatin1String("/") + info.baseName() +
+              info.path() + QLatin1String("/") + info.completeBaseName() +
               QLatin1String(".") +
               selectedExtension; // recreate full filename with chosen suffix
         }