Remove splicing features

After numerous tests it was found the splice features were at best
the same performance as standard IO and at worse actually slower.
To simplify the code all splice features are removed.

src/option_parser.cpp

@@ -122,14 +122,20 @@ should_ignore(const std::string &key_)
 {
   static const std::set<std::string> IGNORED_KEYS =
     {
+      "allow_other",
       "atomic_o_trunc",
       "big_writes",
       "cache.open",
       "defaults",
       "hard_remove",
+      "no_splice_move",
+      "no_splice_read",
+      "no_splice_write",
       "nonempty",
-      "use_ino",
-      "allow_other"
+      "splice_move",
+      "splice_read",
+      "splice_write",
+      "use_ino"
     };
 
   return (IGNORED_KEYS.find(key_) != IGNORED_KEYS.end());
@@ -420,7 +426,7 @@ namespace options
       errs_->push_back({0,"mountpoint not set"});
 
     check_for_mount_loop(cfg,errs_);
-    
+
     set_default_options(args_);
     set_fsname(cfg,args_);
     set_subtype(args_);