[fusl] Update fusl

fusl/src/stdio/fwrite.c

 #include "stdio_impl.h"
 #include <string.h>
 
 size_t __fwritex(const unsigned char *restrict s, size_t l, FILE *restrict f)
 {
         size_t i=0;
 
         if (!f->wend && __towrite(f)) return 0;
 
         if (l > f->wend - f->wpos) return f->write(f, s, l);
 
         if (f->lbf >= 0) {
                 /* Match /^(.*\n|)/ */
                 for (i=l; i && s[i-1] != '\n'; i--);
                 if (i) {
-                        if (f->write(f, s, i) < i)
-                                return i;
+                        size_t n = f->write(f, s, i);
+                        if (n < i) return n;
                         s += i;
                         l -= i;
                 }
         }
 
         memcpy(f->wpos, s, l);
         f->wpos += l;
         return l+i;
 }
 
 size_t fwrite(const void *restrict src, size_t size, size_t nmemb, FILE *restrict f)
 {
         size_t k, l = size*nmemb;
+        if (!size) nmemb = 0;
         FLOCK(f);
         k = __fwritex(src, l, f);
         FUNLOCK(f);
         return k==l ? nmemb : k/size;
 }
 
 weak_alias(fwrite, fwrite_unlocked);