Add leveldb_options_set_max_file_size to the C API.

When the max file size option was added in CL 134391640 the C API
was not modified to support this.

This change was contributed by GitHub user @olt and fixes issue #439.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173466388

db/c.cc

@@ -446,6 +446,10 @@ void leveldb_options_set_block_restart_interval(leveldb_options_t* opt, int n) {
   opt->rep.block_restart_interval = n;
 }
 
+void leveldb_options_set_max_file_size(leveldb_options_t* opt, size_t s) {
+  opt->rep.max_file_size = s;
+}
+
 void leveldb_options_set_compression(leveldb_options_t* opt, int t) {
   opt->rep.compression = static_cast<CompressionType>(t);
 }

db/c_test.c

@@ -189,6 +189,7 @@ int main(int argc, char** argv) {
   leveldb_options_set_max_open_files(options, 10);
   leveldb_options_set_block_size(options, 1024);
   leveldb_options_set_block_restart_interval(options, 8);
+  leveldb_options_set_max_file_size(options, 3 << 20);
   leveldb_options_set_compression(options, leveldb_no_compression);
 
   roptions = leveldb_readoptions_create();

include/leveldb/c.h

@@ -184,6 +184,8 @@ LEVELDB_EXPORT void leveldb_options_set_cache(leveldb_options_t*,
 LEVELDB_EXPORT void leveldb_options_set_block_size(leveldb_options_t*, size_t);
 LEVELDB_EXPORT void leveldb_options_set_block_restart_interval(
     leveldb_options_t*, int);
+LEVELDB_EXPORT void leveldb_options_set_max_file_size(leveldb_options_t*,
+                                                      size_t);
 
 enum {
   leveldb_no_compression = 0,