Shortcut Rational addition if either operand is zero

flower/rational.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 1997--2020 Han-Wen Nienhuys <hanwen@xs4all.nl>
 
   LilyPond is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
   LilyPond is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "rational.hh"
 
 #include <cmath>
 #include <cassert>
 #include <cstdlib>
 
 #include "string-convert.hh"
-#include "libc-extension.hh"
 
 using std::string;
 
 Rational::operator double () const
 {
   if (sign_ == -1 || sign_ == 1 || sign_ == 0)
 // FIXME: workaround: In GUB, g++ 4.9.4 for darwin-x86,
 // it seems that static cast from `unsigned long long` to `double`
 // by x86 SSE2 raises an internal compile error.
 // However, static cast from `signed long long` to `double`
@@ skipping 349 matching lines @@
 sign (Rational r)
 {
   return r.sign ();
 }
 
 bool
 Rational::is_infinity () const
 {
   return sign_ == 2 || sign_ == -2;
 }