editors/yui: partially unbreak with clang 4.0

main.cc:1153:36: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:1768:39: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:1865:35: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:1948:35: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:2030:39: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:2147:39: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf1024, 1023, f ) > 0 ) {
       ~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~

main.cc:2483:37: error: ordered comparison between pointer and zero ('char *' and 'int')

if ( fgets( buf1024, 1023, f ) <= 0 )
     ~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~

main.cc:2618:32: error: ordered comparison between pointer and zero ('char *' and 'int')

while( fgets( buf, 1023, f ) > 0 )
       ~~~~~~~~~~~~~~~~~~~~~ ^ ~

yui1.cc:2668:19: error: ordered comparison between pointer and zero ('FILE *' (aka '__sFILE *') and

'int')
 if ( forig <= 0 ) {
      ~~~~~ ^  ~

yui1.cc:2678:15: error: ordered comparison between pointer and zero ('FILE *' (aka '__sFILE *') and

'int')
     if ( fbak <= 0 ) {
          ~~~~ ^  ~

yui1.cc:2787:15: error: ordered comparison between pointer and zero ('FILE *' (aka '__sFILE *') and

   'int')
if ( forig <= 0 ) {
     ~~~~~ ^  ~

Reported by: antoine (via exp-run)