Blender Git Loki

Some tweaks to support upcoming OSL-1.6

Doesn't mean we're 100% ready for the transition, but need to start somewhere
anyway. Changes:

- OSL is no longer supporting cpp and requires usage of Boost Wave.
So now Wave component of Boost is optionally demanded when looking for the
Boost libraries if OSL is enabled.

Only did this for Linux, MSVC seems already using Wave. Not sure about OSX.

- Because of the same reason OSL should be moved prior Boost for linker.

- Whole archive trick makes it so linking fails with duplicated symbols, so
removed it for the new OSL. Didn't see issues with this so far.

- Added some code to check OSL version on Linux. Would need to move all that
to FindOpenShadingLanguage.cmake which we can get from Cycles standalone
repository.

So in theory no affect on current stup would be made at all.

- Added some tweaks to buildbot files. It now seems to be happy with the new
OSL libraries, but again, those tweaks are not in action yet.

All this was tested on Linux only. Win/OSX might still need some tweaks to
support new OSL.

P.S. This doesn't mean we're pushing OSL update yet, just making some
preliminary tweaks to avoid entropy of PITA when we'll actually want to
switch.