Found the issue causing the effect pictured here. Combination of 2 things:
1 - the shader requirements snuck past what MESA 10.3.2 was capable of (installed fglrx driver - and the several megabytes of cruft that goes along with it! and the general flakeyness of the closed driver!) until MESA 10.4.1 hits the repos, then will test against that. That fixed the texture issues on my avatar and my world.
2 - the ‘rocker’ avatar body is no longer compatible with the render engine - the huge figure in front, once textured, turned out to be the clothing layer (leaving Mr Rocker in his shorts). Fixed by changing to a newer body.
(There might need to be a clean-up of the avatar list - quite a few strait-out crash Interface - eg, FSM - and there are more that no longer render correctly).