wrong key used for signing

[Thomas Danckaert]

I accidentally used the wrong key when signing my commits to 
core-updates yesterday.  How can I fix this? A number of commits were 
already made on top of mine, so we'd need to rebase?

These are the offending commits:

b1a8fd2d2 gnu: libreoffice: Update to 5.3.1.2.
90ac806d3 gnu: orcus: Update to 0.12.1.
b85b56dd7 gnu: libetonyek: Update to 0.1.6.
22e52dbd0 gnu: Add libstaroffice.
cb3864392 gnu: ixion: Update to 0.12.2.
57144094b gnu: mdds: Upgrade to 1.2.2.
741916f11 gnu: Add libzmf.

Thomas