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The DEFS line in MCONFIG had gotten so long that it exceeded 4k, and
this was starting to cause some tools heartburn.  It also made "make
V=1" almost useless, since trying to following the individual commands
run by make was lost in the noise of all of the defines.

So fix this by putting the configure-generated defines in lib/config.h
and the directory pathnames to lib/dirpaths.h.

In addition, clean up some vestigal defines in configure.in and in the
Makefiles to further shorten the cc command lines.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>