Update function documentation to mention stream/attribute limits

Also assert on these limits in JS simplifyWithAttributes; Wasm code
compiles assertions out and this is an important limit right now.

js/meshopt_simplifier.js

@@ -201,6 +201,7 @@ var MeshoptSimplifier = (function() {
 			assert(target_error >= 0 && target_error <= 1);
 			assert(Array.isArray(attribute_weights));
 			assert(vertex_attributes_stride >= attribute_weights.length);
+			assert(attribute_weights.length <= 16);
 
 			var options = 0;
 			for (var i = 0; i < (flags ? flags.length : 0); ++i) {

js/meshopt_simplifier.module.js

@@ -200,6 +200,7 @@ var MeshoptSimplifier = (function() {
 			assert(target_error >= 0 && target_error <= 1);
 			assert(Array.isArray(attribute_weights));
 			assert(vertex_attributes_stride >= attribute_weights.length);
+			assert(attribute_weights.length <= 16);
 
 			var options = 0;
 			for (var i = 0; i < (flags ? flags.length : 0); ++i) {

src/meshoptimizer.h

@@ -67,6 +67,7 @@ MESHOPTIMIZER_API size_t meshopt_generateVertexRemap(unsigned int* destination,
  *
  * destination must contain enough space for the resulting remap table (vertex_count elements)
  * indices can be NULL if the input is unindexed
+ * stream_count must be <= 16
  */
 MESHOPTIMIZER_API size_t meshopt_generateVertexRemapMulti(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count, const struct meshopt_Stream* streams, size_t stream_count);
 
@@ -103,6 +104,7 @@ MESHOPTIMIZER_API void meshopt_generateShadowIndexBuffer(unsigned int* destinati
  * Note that binary equivalence considers all size bytes in each stream, including padding which should be zero-initialized.
  *
  * destination must contain enough space for the resulting index buffer (index_count elements)
+ * stream_count must be <= 16
  */
 MESHOPTIMIZER_API void meshopt_generateShadowIndexBufferMulti(unsigned int* destination, const unsigned int* indices, size_t index_count, size_t vertex_count, const struct meshopt_Stream* streams, size_t stream_count);
 
@@ -354,6 +356,7 @@ MESHOPTIMIZER_API size_t meshopt_simplify(unsigned int* destination, const unsig
  *
  * vertex_attributes should have attribute_count floats for each vertex
  * attribute_weights should have attribute_count floats in total; the weights determine relative priority of attributes between each other and wrt position. The recommended weight range is [1e-3..1e-1], assuming attribute data is in [0..1] range.
+ * attribute_count must be <= 16
  * TODO target_error/result_error currently use combined distance+attribute error; this may change in the future
  */
 MESHOPTIMIZER_EXPERIMENTAL size_t meshopt_simplifyWithAttributes(unsigned int* destination, const unsigned int* indices, size_t index_count, const float* vertex_positions, size_t vertex_count, size_t vertex_positions_stride, const float* vertex_attributes, size_t vertex_attributes_stride, const float* attribute_weights, size_t attribute_count, size_t target_index_count, float target_error, unsigned int options, float* result_error);