[PATCH] x86-64 fixes

[Andrew Cagney]

> It also fixes some calls to malloc() failures. These were evident in
> tests that do stuff like p "foo" or p str_func ("foo") or even simple
> calls like p malloc(2).

Outch!  A working ``(gdb) p malloc(...)'' is pretty fundmental to a 
functional GDB.  Without it, many of the test results are pretty 
meaningless.

This should definitly help stablize the target.

Andrew