C News expire

Unlike the old alpha C News expire, this one will accept old B News history
files... although that slows it down, and this hasn't been tested well.
Beware that the date in the middle field of the history line must be
readable to getdate(3), and rumor hath it that mid-B2.11 dates are not.
Rebuilding your history file in C News format is preferable anyway.
Current releases of B News use C News format, in fact.

It WON'T accept the old experimental C News four-field history files;
we recommend

	awk -F'	' '{ print $1 "	" $2 "~" $3 "	" $4 }'

(those are tabs in the quotes after the -F and the empty-looking quotes
in the awk program) as a conversion aid.

"make r" will compile everything and run a complex set of regression tests,
checking the results automatically.  If nothing screams, there is a high
probability that expire, upact, and mkhistory are working.

dircheck checks the results of expire regression testing.
histdups, histinfo, and histslash are parts of mkhistory.
updatemin is a C version of upact -- it's vastly faster, but it's
	also the only thing in C News that needs to know how to read
	directories, which is a portability hassle, so it's not the default.
	Compile it with -DBERKDIR if you have 4BSD directory functions
	rather than standard (POSIX) ones.  "make r UPACT=updatemin"
	will include it in the regression test.
pgood and tgood are regression-test output-should-look-like-this files.
mkadir is what expire invokes to create archiving subdirectories.
