add support for allow_ingest_behind in C API

Summary:
https://github.com/facebook/rocksdb/wiki/Creating-and-Ingesting-SST-files

Need to expose these functions in the C API to be used by Go bindings.
Closes https://github.com/facebook/rocksdb/pull/3011

Differential Revision: D6679563

Pulled By: sagar0

fbshipit-source-id: 536f844ddaeb0172c6d7e416d2a75e8f9e57c8ef

db/c.cc

@@ -1999,6 +1999,11 @@ void rocksdb_options_optimize_universal_style_compaction(
   opt->rep.OptimizeUniversalStyleCompaction(memtable_memory_budget);
 }
 
+void rocksdb_options_set_allow_ingest_behind(
+    rocksdb_options_t* opt, unsigned char v) {
+  opt->rep.allow_ingest_behind = v;
+}
+
 void rocksdb_options_set_compaction_filter(
     rocksdb_options_t* opt,
     rocksdb_compactionfilter_t* filter) {

include/rocksdb/c.h

@@ -710,6 +710,9 @@ extern ROCKSDB_LIBRARY_API void rocksdb_options_optimize_level_style_compaction(
 extern ROCKSDB_LIBRARY_API void
 rocksdb_options_optimize_universal_style_compaction(
     rocksdb_options_t* opt, uint64_t memtable_memory_budget);
+extern ROCKSDB_LIBRARY_API void
+rocksdb_options_set_allow_ingest_behind(rocksdb_options_t*,
+                                                   unsigned char);
 extern ROCKSDB_LIBRARY_API void rocksdb_options_set_compaction_filter(
     rocksdb_options_t*, rocksdb_compactionfilter_t*);
 extern ROCKSDB_LIBRARY_API void rocksdb_options_set_compaction_filter_factory(