emulators/fceux: unbreak with clang 4.0

fceux-server/server.cpp:117:29: error: ordered comparison between pointer and zero

    ('char *' and 'int')
while(fgets(buf, 256, fp) > 0)
      ~~~~~~~~~~~~~~~~~~~ ^ ~

src/cheat.cpp:219:30: error: ordered comparison between pointer and zero ('char *' and 'int')

while(fgets(linebuf,2048,fp)>0)
      ~~~~~~~~~~~~~~~~~~~~~~^~

Reported by: antoine (via exp-run)