Consistently include Makeconfig after defining subdir.

In <https://sourceware.org/ml/libc-alpha/2014-01/msg00196.html> I
noted it was necessary to add includes of Makeconfig early in various
subdirectory makefiles for the tests-special variable settings added
by that patch to be conditional on configuration information.  No-one
commented on the general question there of whether Makeconfig should
always be included immediately after the definition of subdir.

This patch implements that early inclusion of Makeconfig in each
directory (which is a lot easier than consistent placement of includes
of Rules).  Includes are added if needed, or moved up if already
present.  Subdirectory "all:" targets are removed, since Makeconfig
provides one.

There is potential for further cleanups I haven't done.  Rules and
Makerules have code such as

ifneq   "$(findstring env,$(origin headers))" ""
headers :=
endif

to override to empty any value of various variables that came from the
environment.  I think there is a case for Makeconfig setting all the
subdirectory variables (other than subdir) to empty to ensure no
outside value is going to take effect if a subdirectory fails to
define a variable.  (A list of such variables, possibly out of date
and incomplete, is in manual/maint.texi.)  Rules and Makerules would
give errors if Makeconfig hadn't already been included, instead of
including it themselves.  The special code to override values coming
from the environment would then be obsolete and could be removed.

Tested x86_64, including that installed binaries are identical before
and after the patch.

	* argp/Makefile: Include Makeconfig immediately after defining
	subdir.
	* assert/Makefile: Likewise.
	* benchtests/Makefile: Likewise.
	* catgets/Makefile: Likewise.
	* conform/Makefile: Likewise.
	* crypt/Makefile: Likewise.
	* csu/Makefile: Likewise.
	(all): Remove target.
	* ctype/Makefile: Include Makeconfig immediately after defining
	subdir.
	* debug/Makefile: Likewise.
	* dirent/Makefile: Likewise.
	* dlfcn/Makefile: Likewise.
	* gmon/Makefile: Likewise.
	* gnulib/Makefile: Likewise.
	* grp/Makefile: Likewise.
	* gshadow/Makefile: Likewise.
	* hesiod/Makefile: Likewise.
	* hurd/Makefile: Likewise.
	(all): Remove target.
	* iconvdata/Makefile: Include Makeconfig immediately after
	defining subdir.
	* inet/Makefile: Likewise.
	* intl/Makefile: Likewise.
	* io/Makefile: Likewise.
	* libio/Makefile: Likewise.
	(all): Remove target.
	* locale/Makefile: Include Makeconfig immediately after defining
	subdir.
	* login/Makefile: Likewise.
	* mach/Makefile: Likewise.
	(all): Remove target.
	* malloc/Makefile: Include Makeconfig immediately after defining
	subdir.
	(all): Remove target.
	* manual/Makefile: Include Makeconfig immediately after defining
	subdir.
	* math/Makefile: Likewise.
	* misc/Makefile: Likewise.
	* nis/Makefile: Likewise.
	* nss/Makefile: Likewise.
	* po/Makefile: Likewise.
	(all): Remove target.
	* posix/Makefile: Include Makeconfig immediately after defining
	subdir.
	* pwd/Makefile: Likewise.
	* resolv/Makefile: Likewise.
	* resource/Makefile: Likewise.
	* rt/Makefile: Likewise.
	* setjmp/Makefile: Likewise.
	* shadow/Makefile: Likewise.
	* signal/Makefile: Likewise.
	* socket/Makefile: Likewise.
	* soft-fp/Makefile: Likewise.
	* stdio-common/Makefile: Likewise.
	* stdlib/Makefile: Likewise.
	* streams/Makefile: Likewise.
	* string/Makefile: Likewise.
	* sunrpc/Makefile: Likewise.
	(all): Remove target.
	* sysvipc/Makefile: Include Makeconfig immediately after defining
	subdir.
	* termios/Makefile: Likewise.
	* time/Makefile: Likewise.
	* timezone/Makefile: Likewise.
	(all): Remove target.
	* wcsmbs/Makefile: Include Makeconfig immediately after defining
	subdir.
	* wctype/Makefile: Likewise.

libidn/ChangeLog:
	* Makefile: Include Makeconfig immediately after defining subdir.

localedata/ChangeLog:
	* Makefile: Include Makeconfig immediately after defining subdir.
	(all): Remove target.

nptl/ChangeLog:
	* Makefile: Include Makeconfig immediately after defining subdir.

nptl_db/ChangeLog:
	* Makefile: Include Makeconfig immediately after defining subdir.