Added wxBackingFile and wxBackedInputStream.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42279 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/chkconf.h

@@ -83,6 +83,14 @@
    please keep the options in alphabetical order!
  */
 
+#ifndef wxUSE_BACKINGFILE
+#   ifdef wxABORT_ON_CONFIG_ERROR
+#       error "wxUSE_BACKINGFILE must be defined."
+#   else
+#       define wxUSE_BACKINGFILE 0
+#   endif
+#endif /* !defined(wxUSE_BACKINGFILE) */
+
 #ifndef wxUSE_CRASHREPORT
     /* this one is special: as currently it is Windows-only, don't force it
        to be defined on other platforms */
@@ -1160,6 +1168,17 @@
 #   endif
 #endif /* wxUSE_ZIPSTREAM */
 
+#if wxUSE_BACKINGFILE
+#   if !wxUSE_STREAMS || (!wxUSE_FILE && !wxUSE_FFILE)
+#       ifdef wxABORT_ON_CONFIG_ERROR
+#           error "wxBackingFile requires wxStream and wxFile or wxFFile"
+#       else
+#           undef wxUSE_BACKINGFILE
+#           define wxUSE_BACKINGFILE 1
+#       endif
+#   endif
+#endif /* wxUSE_ZIPSTREAM */
+
 /* the rest of the tests is for the GUI settings only */
 #if wxUSE_GUI