Clean up library dependencies

Clean up library dependencies

Move stuff to untangle the ugly cyclic dependencies between the
archives built for selected subdirectories of src/lib/:

* Move common/io.c to empthread/ because it requires empthread stuff

* Move parts of subs/nstr.c to common/nstreval.c to satisfy
  common/ef_verify.o

* Move getstarg.c getstring.c onearg.c from gen/ to subs/ because they
  require stuff from there

* Move bridgefall.c check.c damage.c empobj.c journal.c maps.c
  sectdamage.c from common/ to subs/ because they require stuff from
  there

* Move cnumb.c from subs/ to common/ to satisfy common/type.o

* Move log.c fsize.c from common/ to gen/ because they really belong
  there

* Move emp_config.c mapdist.c from gen/ to common/ because they really
  belong there, and require stuff from libglobal.a

Also package as/ as libas.a to satisfy common/path.o.

Remaining dependencies:

    lib             needs
    --------------------------------------------
    libas.a         libglobal.a
    libcommon.a     libas.a libglobal.a libgen.a
    libgen.a
    libglobal.a
    liblwp.a        libgen.a
    libw32.a[*]     libgen.a

    [*] Except for service.o, which can only be linked into the server

Link order now: liblwp.a libcommon.a libas.a libgen.a libglobal.a
libw32.a.  The position of libw32.a is not quite right, but works
anyway.