perl5.000 patch.0o: [address] a few more Configure and build nits.

perl5.000 patch.0o: [address] a few more Configure and build nits.

This patch addresses a few more Configure and build nits.  Full
details are given below, but the main hightligths are (slightly)
better support for nested extensions and DLD and AIX MakeMaker fixes.

Configure
        Detect MachTen.  Thanks to Mark Pease <peasem@primenet.com>.
        Delete some tabs that caused a MachTen /bin/sh core dump!
        Detect extensions nested 1 level deep, e.g.  Devel/DProf/DProf.xs

MANIFEST
MANIFEST.new
        Include new hints/machten.sh hint file.

Makefile.SH
        Document why we use ./makedir instead of mkdir.

U/Extensions.U
        Detect extensions nested 1 level deep, e.g.  Devel/DProf/DProf.xs

U/dist3_051.pat
        Include MachTen patches.

configpm
        Convert nested extension names from filesytem-dependent Devel/DProf
        to perl5's internal naming scheme Devel::DProf.

doio.c
        A dup-related buglet fix from Hallvard B. Furuseth
        <h.b.furuseth@usit.uio.no>.

ext/DB_File/DB_File.pm
ext/DynaLoader/DynaLoader.pm
ext/Fcntl/Fcntl.pm
ext/GDBM_File/GDBM_File.pm
ext/POSIX/POSIX.pm
ext/Socket/Socket.pm
        Throw a qw() around @ISA elements to show "good style".

hints/machten.sh
        new file.

lib/ExtUtils/MakeMaker.pm
        Bump version number to 4.086.
        Fix AIX buglet -- needed to specify NAME.
        Linux/DLD/gcc-2.6.2:  We no longer load .sa libraries (except
        libm.sa, which is apparently still o.k.

util.c
        Another dup-related buglet fix.