[Ada] Fix errno for rename for the VxWorks 6 target

[Ada] Fix errno for rename for the VxWorks 6 target

This fixes the wrong errno for rename when the file is not existing on a
dosFs. In the end it makes Ada.Directories.Rename raising the right
exception in the case we are trying to move a file in a non existing
directory.

2019-09-18  Frederic Konrad  <konrad@adacore.com>

gcc/ada/

	* adaint.c: Include dosFsLib.h and vwModNum.h for VxWorks 6.
	(__gnat_rename): Map S_dosFsLib_FILE_NOT_FOUND to ENOENT.

From-SVN: r275846