Serf / libsvn_ra_serf doesn't work with Squid-fronted Apache

Serf / libsvn_ra_serf doesn't work with Squid-fronted Apache:

$ svn ls http://overlaystest.gentoo.org/svn/proj/python
svn: XML parsing failed: (411 Length Required)
$

This problem was originally reported in:
https://bugs.gentoo.org/show_bug.cgi?id=241234

Robin Johnson <robbat2_at_gentoo.org> wrote in that bug report:
> Doing a tcpdump on during the co request, and comparing the requests, the Neon
> version sends PROPFIND with Content-Length, while serf sends PROPFIND without
> Content-Length, which thus upsets squid.

-- 
Arfrever Frehtes Taifersar Arahesis