svnimport: add support for parsing From: lines for author

svnimport: add support for parsing From: lines for author

When commiting a non-signed off contribution you cannot just add
a Signed-off-by: from the author as they did not sign it off.
But if you then commit it, and necessarily sign it off yourself,
the change appears to be yours.  In this case it is common to use
the following form:

	Commentry

	From: originator <email>
	Signed-of-by: me <my email>
Now that we have support for parsing Signed-off-by: for author
information it makes sense to handle From: as well.  This patch
adds a new -F which will handle From: lines in the comments.  It
may be used in combination with -S.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>