InnoDB portability fix: new function os_file_set_eof()

innobase/include/os0file.h:
  Add os_file_set_eof()
innobase/os/os0file.c:
  Add os_file_set_eof()
innobase/srv/srv0srv.c:
  Replace chsize() or ftruncate() with os_file_set_eof()
sql/ha_innodb.cc:
  Replace my_chsize() with os_file_set_eof()

innobase/os/os0file.c

@@ -1031,6 +1031,23 @@ error_handling:
 	return(FALSE);
 }
 
+/***************************************************************************
+Truncates a file at its current position. */
+
+ibool
+os_file_set_eof(
+/*============*/
+				/* out: TRUE if success */
+	FILE*		file)	/* in: file to be truncated */
+{
+#ifdef __WIN__
+	HANDLE h = (HANDLE) _get_osfhandle(fileno(file));
+	return(SetEndOfFile(h));
+#else /* __WIN__ */
+	return(!ftruncate(fileno(file), ftell(file)));
+#endif /* __WIN__ */
+}
+
 /***************************************************************************
 Flushes the write buffers of a given file to the disk. */