Enable DWARF unwinders for SPU

Enable DWARF unwinders for SPU

This patch enables use of DWARF unwinders for the SPU target.

In addition to appending the DWARF unwinders, we also need to install
a spu_dwarf_reg_to_regnum that maps the raw stack pointer register to
the cooked version (to avoid mismatches with gdbarch_sp_regnum).

This also causes confusion with the AX collect handling, so we also
install ax_pseudo_register routines to handle the cooked SP.

gdb/
2014-04-17  Ulrich Weigand  <uweigand@de.ibm.com>

	* spu-tdep.c: Include "dwarf2-frame.h" and "ax.h".
	(spu_ax_pseudo_register_collect): New function.
	(spu_ax_pseudo_register_push_stack): Likewise.
	(spu_dwarf_reg_to_regnum): Likewise.
	(spu_gdbarch_init): Install them.  Append DWARF unwinders.