hgweb: working diff for removed files

hgweb: remove links to non-existent file versions

coal/paper: widen author column in log table

hgweb: be sure to drain request data even in early error conditions Thanks to Mads Kiilerich with noticing this. The hg client can only read data after all the sent data has been read, so we have to read all the request data even if we're not going to do anything with it (in error conditions). This is not easy to fix in the client, because we're using Python's httplib, which is strictly stateful. Abstracted the draining into a separate method.

merge with crew-stable

Fix Debian bug #494889 (fetching from static-http://... broken) Changeset 6605a03cbf87 which fixed issue965 (hg clone static-http does not work for empty repos) broke cloning of repos with old layout (without store) via static-http. This fix makes cloning from old-style repositories possible again, but will not allow cloning of empty old-style repositories as this can not be detected reliably.