convert to_thread_address_space to use TARGET_DEFAULT_FUNC

This converts to_thread_address_space to use TARGET_DEFAULT_FUNC.

This method was one of a handful not using the normal target
delegation approach.  The only rationale here is consistency in the
target vector.

Built and regtested on x86-64 Fedora 20.

2014-06-04  Tom Tromey  <tromey@redhat.com>

	* target-delegates.c: Rebuild.
	* target.c (default_thread_address_space): New function.
	(target_thread_address_space): Simplify.
	* target.h (struct target_ops) <to_thread_address_space>: Add
	TARGET_DEFAULT_FUNC.
constify to_attach

This constifies the "args" argument to the target_ops to_attach
method.

I updated all instances of the method.  I could not compile all of
them but I hand-inspected them.  In all cases either the argument is
ignored, or it is passed to parse_pid_to_attach.  (linux-nat does some
extra stuff, but that one I built...)

If you want to try it on your host of choice, please do so.

The code in parse_pid_to_attach seems a little bogus to me.  If there
is a platform with a broken strtoul, we have better methods for fixing
the issue now.  However, I left the code as is since it is clearly ok
to do so.

Built and regtested on x86-64 Fedora 20.

2014-06-04  Tom Tromey  <tromey@redhat.com>

	* procfs.c (procfs_attach): Make "args" const.
	* windows-nat.c (windows_attach): Make "args" const.
	* nto-procfs.c (procfs_attach): Make "args" const.
	* inf-ttrace.c (inf_ttrace_attach): Make "args" const.
	* go32-nat.c (go32_attach): Make "args" const.
	* gnu-nat.c (gnu_attach): Make "args" const.
	* darwin-nat.c (darwin_attach): Make "args" const.
	* inf-ptrace.c (inf_ptrace_attach): Make "args" const.
	* linux-nat.c (linux_nat_attach): Make "args" const.
	* remote.c (extended_remote_attach_1, extended_remote_attach):
	Make "args" const.
	* target.h (struct target_ops) <to_attach>: Make "args" const.
	(find_default_attach): Likewise.
	* utils.c (parse_pid_to_attach): Make "args" const.
	* utils.h (parse_pid_to_attach): Update.