Add rs6000/xilinx.h -- missed in earlier checkin.

From-SVN: r146633

gcc/config/rs6000/xilinx.h

+/* Support for GCC on Xilinx embedded PowerPC systems
+   Copyright (C) 2008 Free Software Foundation, Inc.
+   Contributed by Michael Eager, eager@eagercon.com
+
+   This file is part of GCC.
+
+   GCC is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3, or (at your
+   option) any later version.
+
+   GCC is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+   License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Set defaults for Xilinx embedded target boards. */
+
+#undef	LIB_DEFAULT_SPEC
+#define LIB_DEFAULT_SPEC "\
+%{!nostdlib: --start-group -lxil -lc -lm --end-group   \
+%{mppcperflib: %{mfpu=*: -lppcstr405 -lgcc}            \
+%{!mfpu=*: -lppcstr405 -lppcfp -lgcc}}                 \
+%{!mppcperflib: -lgcc}}"
+
+#undef	STARTFILE_DEFAULT_SPEC
+#define STARTFILE_DEFAULT_SPEC "\
+ecrti.o%s %{pg: %{!mno-clearbss: xil-pgcrt0.o%s} \
+%{mno-clearbss: xil-sim-pgcrt0.o%s}}            \
+%{!pg: %{!mno-clearbss: xil-crt0.o%s}           \
+%{mno-clearbss: xil-sim-crt0.o%s}} crtbegin.o%s"
+
+#undef	LINK_START_DEFAULT_SPEC
+#define LINK_START_DEFAULT_SPEC "-T xilinx.ld%s"