Merge branch 'check-headers-max-warn'

Check compilation of all wx headers with all gcc warnings enabled.

This should make it impossible to introduce problems that only appear
when -Wpedantic or -Wany-other-not-completely-unreasonable-warning is
enabled when building user code including wx headers again.

See https://github.com/wxWidgets/wxWidgets/pull/2033

include/wx/generic/grid.h

@@ -1140,9 +1140,9 @@ private:
     {
     }
 
-    wxGridBlocks(iterator_impl begin, iterator_impl end) :
-        m_begin(begin),
-        m_end(end)
+    wxGridBlocks(iterator_impl ibegin, iterator_impl iend) :
+        m_begin(ibegin),
+        m_end(iend)
     {
     }