Squashed feature branch:

* Added CUDA support
 * Performance improvements
 * API improvements
 * Added "depth" parameter to GEMM
 * Android cross-compilation

lib/backend/keywords.cpp

@@ -0,0 +1,29 @@
+#include "isaac/backend/keywords.h"
+
+namespace isaac
+{
+
+keyword::keyword(driver::backend_type backend, std::string const & opencl, std::string const & cuda) : backend_(backend), opencl_(opencl), cuda_(cuda)
+{
+
+}
+
+std::string const & keyword::get() const
+{
+  switch(backend_)
+  {
+    case driver::OPENCL: return opencl_;
+#ifdef ISAAC_WITH_CUDA
+    case driver::CUDA: return cuda_;
+#endif
+    default: throw;
+  }
+}
+
+std::ostream &  operator<<(std::ostream & ss, keyword const & kw)
+{
+  return ss << kw.get();
+}
+
+
+}