Grib plugin ignores app-wide screen size settings

[nohal]

OpenCPN/plugins/grib_pi/src/GribOverlayFactory.cpp

Lines 240 to 250 in cceeff7

	if(wxGetDisplaySize().x > 0){
	#ifdef __WXGTK__
	GdkScreen *screen = gdk_screen_get_default();
	m_pixelMM = (double)gdk_screen_get_monitor_width_mm(screen, 0) / wxGetDisplaySize().x;
	#else
	m_pixelMM = (double)wxGetDisplaySizeMM().x / wxGetDisplaySize().x;
	#endif
	m_pixelMM = wxMax(.02, m_pixelMM); // protect against bad data
	}
	else
	m_pixelMM = 0.27; // semi-standard number...

Should be replaced with logic following the screen width setting in the core application preferences.