This changeset makes sparc64_linux_step_trap to return 0 when a

This changeset makes sparc64_linux_step_trap to return 0 when a
breakpoint is set in a `ta 0x6d´ which is not a sigreturn syscall.  In
these cases no rt_frame exists in the stack and thus the read PC is
wrong.

ChangeLog
2014-01-29  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* sparc64-linux-tdep.c (sparc64_linux_step_trap): Get PC from
          the sigreturn register save area only if the syscall is
          sigreturn.

testsuite/ChangeLog
2014-01-29  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* gdb.arch/sparc-sysstep.exp: New file.
	* gdb.arch/sparc-sysstep.c: Likewise.

	* gdb.arch/Makefile.in (EXECUTABLES): Add sparc-sysstep.