Add support for multiple interpolation modes on cycles image textures

All textures are sampled bi-linear currently with the exception of OSL there texture sampling is fixed and set to smart bi-cubic.

This patch adds user control to this setting.

Added:
- bits to DNA / RNA in the form of an enum for supporting multiple interpolations types
- changes to the image texture node drawing code ( add enum)
- to ImageManager (this needs to know to allocate second texture when interpolation type is different)
- to node compiler (pass on interpolation type)
- to device tex_alloc this also needs to get the concept of multiple interpolation types
- implementation for doing non interpolated lookup for cuda and cpu
- implementation where we pass this along to osl ( this makes OSL also do linear untill I add smartcubic to the interface / DNA/ RNA)

Reviewers: brecht, dingto

Reviewed By: brecht

CC: dingto, venomgfx

Differential Revision: https://developer.blender.org/D317

intern/cycles/kernel/kernel.cpp

@@ -37,7 +37,7 @@ void kernel_const_copy(KernelGlobals *kg, const char *name, void *host, size_t s
 		assert(0);
 }
 
-void kernel_tex_copy(KernelGlobals *kg, const char *name, device_ptr mem, size_t width, size_t height)
+void kernel_tex_copy(KernelGlobals *kg, const char *name, device_ptr mem, size_t width, size_t height, InterpolationType interpolation)
 {
 	if(0) {
 	}
@@ -63,6 +63,7 @@ void kernel_tex_copy(KernelGlobals *kg, const char *name, device_ptr mem, size_t
 			tex->data = (float4*)mem;
 			tex->width = width;
 			tex->height = height;
+			tex->interpolation = interpolation;
 		}
 	}
 	else if(strstr(name, "__tex_image")) {
@@ -78,6 +79,7 @@ void kernel_tex_copy(KernelGlobals *kg, const char *name, device_ptr mem, size_t
 			tex->data = (uchar4*)mem;
 			tex->width = width;
 			tex->height = height;
+			tex->interpolation = interpolation;
 		}
 	}
 	else