Update: Manning's contract was merely adjusted to include an insurance policy for the team.
Late Thursday evening, it was discovered—and pointed out by many folks on Twitter—that NFL.com/Transactions had recorded a renegotiated signed contract between quarterback Peyton Manning and the Denver Broncos.
Such an occurrence would be a huge story, which makes it surprising that there has been no confirmation (or denial) of the report from the media or the team as of early Friday morning. It may have been a mistake or some form of a typo, but NFL.com's transaction page presumably is fed information straight from the teams.
And the #Broncos may have just created more cap room: nfl.com/transactions says Peyton Manning signed a renegotiated contract on Thursday.
— Jon Heath (@JHSMDEN) May 17, 2013
Until the report is confirmed (or debunked), consider it just a rumor (even if it was created by NFL.com).