hgweb: add nextentry variable for easy pagination in changelog nextentry always contains the first entry not shown on current page (if there is such entry)

hgweb: always compute all entries and latestentry in changelog Get the whole list of entries before rendering instead of using lazy evaluation. This doesn't affect the performance for usual case when the entries are shown anyway. When both entries and latestentry are used, this performs unnoticeably faster, and for pages which use only latestentry (quite uncommon case) it would be a bit slower. This change will make it possible to get the first entry of the next page easily without computing the list twice.

templatefilters: add short format for age formatting Implements a short output format for ages e.g. "1 second ago" is abbrevated as "1s ago".

hgweb: remove unused argument of changelist function in changelog This doesn't change the behavior as the argument isn't used anyway, and it's a preparation to the next patches,