wx: check WXE_WEBVIEW before include wx/webview.h

There are cases where wx/configure.ac detects that wxwidgets
does not have support for webview.

Author: joaohf

lib/wx/c_src/gen/wxe_macros.h

@@ -71,10 +71,12 @@
 #include <wx/sysopt.h>
 #include <wx/overlay.h>
 #include <wx/notifmsg.h>
+#if WXE_WEBVIEW
 #include <wx/webview.h>
 #if wxUSE_WEBVIEW && wxUSE_WEBVIEW_IE
 #include <wx/msw/webview_ie.h>
 #endif
+#endif
 #if wxUSE_GLCANVAS_EGL && !wxCHECK_VERSION(3,2,3)
 #include <EGL/egl.h>
 #endif