is in accordance with the information provided at
ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
Also add $FreeBSD$ to a few files to keep svn happy.
Discussed with: imp, rwatson
Add some constness to avoid some warnings.
Remove use register keyword.
Deal with missing/unneeded extern/prototypes.
Some minor type changes/casts to avoid warnings.
Reviewed by: md5
for remaining arguments, rather than checking for *argv being a boolean truth.
Instead of using an empty case to check for -f- to mean "read stdin", and have
stdin reopned otherwise, use a FILE* for the mbox, and assign it to stdin when
we mean to use stdin, otherwise fopen(3). Kill `register' qualifier.