Ok, I set up a context in one of my localhost installations, "localhost/revo233/testing/". After some initial fumbling, the XRouter plugin worked perfectly.
'web' context settings (taken from actual setting tag output, e.g. [[++http_host]]):
http_host: localhost
site_url: http://localhost/revo233/
base_url: /revo233/
site_start: 1
'testing' context settings:
http_host: localhost
base_url: /revo233/testing/
site_start: 24
Then in System Settings I changed "link_tag_scheme" to "abs", and in my pdoMenu snippet I added the &scheme=`abs` property to get the menus generated correctly.
[[pdoMenu?
&parents=`0`
&level=`1`
&outerClass=`nav navbar-nav navbar-right`
&firstClass=`first hidden`
&scheme=`abs`
]]