Use wxHAS_IMAGES_IN_RESOURCES instead of explicit platform checks.

Add a special symbol which is defined only if the icons and other images (e.g.
cursor) are in the separate resource files and don't need to be embedded as
XPMs in the main program.

This makes the checks more clear and more customizable as it's enough to
change wxHAS_IMAGES_IN_RESOURCES definition instead of changing many platform
checks.

Closes #14050.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70789 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/mainpages/const_cpp.h

@@ -214,6 +214,8 @@ Currently the following symbols exist:
     decide whether some function should be overloaded for both
     <code>long</code> and <code>long long</code> types.}
 @itemdef{wxHAS_MULTIPLE_FILEDLG_FILTERS, Defined if wxFileDialog supports multiple ('|'-separated) filters.}
+@itemdef{wxHAS_IMAGES_IN_RESOURCES, Defined if <a href="http://en.wikipedia.org/wiki/Resource_(Windows)">
+    Windows resource files</a> or OS/2 resource files are available on the current platform.}
 @itemdef{wxHAS_POWER_EVENTS, Defined if wxPowerEvent are ever generated on the current platform.}
 @itemdef{wxHAS_RADIO_MENU_ITEMS,
         Defined if the current port supports radio menu items (see wxMenu::AppendRadioItem).}