Take compression level_values as const pointer (#9376)

Summary:
Compatible change, more natural (especially in generated Rust bindings), no risk that the API will ever need mutable access because it has to make a copy anyway.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9376

Reviewed By: ajkr

Differential Revision: D33541435

Pulled By: pdillinger

fbshipit-source-id: 15c512a0d70b6e8694fa99d598b7d022751c1e59

db/c.cc

@@ -2834,7 +2834,7 @@ int rocksdb_options_get_bottommost_compression(rocksdb_options_t* opt) {
 }
 
 void rocksdb_options_set_compression_per_level(rocksdb_options_t* opt,
-                                               int* level_values,
+                                               const int* level_values,
                                                size_t num_levels) {
   opt->rep.compression_per_level.resize(num_levels);
   for (size_t i = 0; i < num_levels; ++i) {

include/rocksdb/c.h

@@ -950,7 +950,7 @@ extern ROCKSDB_LIBRARY_API void rocksdb_options_set_merge_operator(
 extern ROCKSDB_LIBRARY_API void rocksdb_options_set_uint64add_merge_operator(
     rocksdb_options_t*);
 extern ROCKSDB_LIBRARY_API void rocksdb_options_set_compression_per_level(
-    rocksdb_options_t* opt, int* level_values, size_t num_levels);
+    rocksdb_options_t* opt, const int* level_values, size_t num_levels);
 extern ROCKSDB_LIBRARY_API void rocksdb_options_set_create_if_missing(
     rocksdb_options_t*, unsigned char);
 extern ROCKSDB_LIBRARY_API unsigned char rocksdb_options_get_create_if_missing(