fix: Correct macOS dynamic lib extension

Author: gcarreno

src/leveldb.common.pas

@@ -56,7 +56,7 @@   leveldb_writeoptions_t = record end;
   libname = 'libleveldb.dll'; // May have a different name
 {$ENDIF}
 {$IFDEF DARWIN}
-  libname = 'libleveldb.???'; // May have a different name
+  libname = 'libleveldb.dylib'; // May have a different name
 {$ENDIF}
   // Status codes
   LEVELDB_OK = 0;