Add support for bit depth with raw input and output (#2762)

* Determine input raw pixel depth from the given typed array
* Allow pixel depth to be set on raw output

src/pipeline.h

@@ -169,6 +169,7 @@ struct PipelineBaton {
   int heifSpeed;
   std::string heifChromaSubsampling;
   bool heifLossless;
+  VipsBandFormat rawDepth;
   std::string err;
   bool withMetadata;
   int withMetadataOrientation;
@@ -298,6 +299,7 @@ struct PipelineBaton {
     heifSpeed(5),
     heifChromaSubsampling("4:4:4"),
     heifLossless(false),
+    rawDepth(VIPS_FORMAT_UCHAR),
     withMetadata(false),
     withMetadataOrientation(-1),
     withMetadataDensity(0.0),