line numbers in multiple preformatted blocks always link to the first (BB-1436)

If a wiki page contains several preformatted blocks, the line numbers all link to the first appearance of that line number on the page.

In other words, it's not possible to link to a specific line number in anything other than the first block (assuming it's longer than all other blocks on the page).

To reproduce, preview the following on any wiki page and click the second line number:
{{{
{{{
#!ini
test=123
}}}
test
{{{
#!ini
test=456
}}}
}}}

Seems to be a case of just generating link names with a number for each block (eg cl-1-1, cl-2-1).