1.3.0

• API breaking change: vex::purge_kernel_caches() family of functions is
  renamed to vex::purge_caches() as the online cache now may hold objects of
  arbitrary type. The overloads that used to take
  vex::backend::kernel_cache_key now take const vex::backend::command_queue&.
• The online cache is now purged whenever vex::Context is destroyed. This
  allows for clean release of OpenCL/CUDA contexts.
• Code for random number generators has been unified between OpenCL and CUDA
  backends.
• Fast Fourier Transform is now supported both for OpenCL and CUDA backends.
• vex::backend::kernel constructor now takes optional parameter with command
  line options.
• Performance of CLOGS algorithms has been improved.
• VEX_BUILTIN_FUNCTION macro has been made public.
• Minor bug fixes and improvements.