Jumping scroll when loading Local Definitions

[clangen2]

When looking at a list with local definitions, some sections get skipped.
Example: https://bridge.haverford.edu/select/Latin/result/vergil_aeneid/4.1-4.89/non_running/ (on my screen it happens around line 14, which is followed by line 28 instead of 15, will vary with different screens).
This is because clusterize anticipates that row heights will be more or less the same. For our short (and the vast majority of our long) definitions, this is not an issue. But many local common definitions are too long, and make their rows too tall; this is then used to infer the height of other rows that are a more normal height. Long term we can work on making them more concise, and with the new organization of texts, more precise. Messing with the rows_in_block and blocks_in_cluster variables may be able to hide this problem.