gitweb: Fix blob linenr links in pathinfo mode

In pathinfo mode, we use <base href> that refers to the base location
of gitweb in order for various external media links to work well.
However, this means that for the page to refer to itself, it must
regenerate full link, and this is exactly what the blob view page
did not do for line numbers.

Signed-off-by: Petr Baudis <redacted>
Signed-off-by: Junio C Hamano <redacted>