Add wxHAS_BITMAPTOGGLEBUTTON and test for it in the unit test.

Not all ports define wxBitmapToggleButton class currently, so add a special
symbol which is defined only if this class is indeed available and test for it
in the unit test for this class.

This fixes the tests compilation under wxX11.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65706 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/mainpages/const_cpp.h

@@ -196,6 +196,8 @@ Currently the following symbols exist:
     have an efficient (CPU-specific) implementation. Notice that the functions
     themselves are always available but can be prohibitively slow to use when
     implemented in a generic way, using a critical section.}
+@itemdef{wxHAS_BITMAPTOGGLEBUTTON, Defined in @c wx/tglbtn.h if
+    wxBitmapToggleButton class is available in addition to wxToggleButton.}
 @itemdef{wxHAS_CONFIG_TEMPLATE_RW, Defined if the currently used compiler
     supports template Read() and Write() methods in wxConfig.}
 @itemdef{wxHAS_LARGE_FILES, Defined if wxFile supports files more than 4GB in