Reduce minimum-width to 800px

Tested in a VirtualBox setup with screen set to 800x600,
all of the Generic Linux RT components are visible, and
the buttons are too (which fall off the screen otherwise).

FIXES #731

src/calamares/CalamaresWindow.cpp

@@ -46,10 +46,13 @@ CalamaresWindow::CalamaresWindow( QWidget* parent )
                               string( Calamares::Branding::ProductName ) ) );
     )
 
-    setMinimumSize( 1010, 520 );
+    constexpr int min_w = 800;
+    constexpr int min_h = 520;
+
+    setMinimumSize( min_w, min_h );
     QSize availableSize = qApp->desktop()->availableGeometry( this ).size();
-    int w = qBound( 1010, CalamaresUtils::defaultFontHeight() * 60, availableSize.width() );
+    int w = qBound( min_w, CalamaresUtils::defaultFontHeight() * 60, availableSize.width() );
-    int h = qBound( 520,  CalamaresUtils::defaultFontHeight() * 36, availableSize.height() );
+    int h = qBound( min_h,  CalamaresUtils::defaultFontHeight() * 36, availableSize.height() );
 
     cDebug() << "Proposed window size:" << w << h;
     resize( w, h );