added wxTempFile::Flush() (dedicated to Theodore Ts'o and Ext4)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60830 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/file.h

@@ -129,6 +129,18 @@ public:
     */
     void Discard();
 
+    /**
+        Flush the data written to the file to disk.
+
+        This simply calls wxFile::Flush() for the underlying file and may be
+        necessary with file systems such as XFS and Ext4 under Linux. Calling
+        this function may however have serious performance implications and
+        also is not necessary with many other file systems so it is not done by
+        default -- but you can call it before calling Commit() to absolutely
+        ensure that the data was indeed written to the disk correctly.
+     */
+    bool Flush();
+
     /**
         Returns @true if the file was successfully opened.
     */