Support NUL containing lines in head(1)

Very trivial this time.

README

@@ -40,7 +40,7 @@ The following tools are implemented:
  #*|o fold            .
 0=*|o getconf         (-v)
  =*|o grep            .
- =*|o head            .
+0=*|o head            .
 0=*|x hostname        .
 0=*|x install         .
  =* o join            .

head.c

@@ -14,7 +14,7 @@ head(FILE *fp, const char *fname, size_t n)
 	ssize_t len;
 
 	while (i < n && (len = getline(&buf, &size, fp)) > 0) {
-		fputs(buf, stdout);
+		fwrite(buf, 1, len, stdout);
 		i += (len && (buf[len - 1] == '\n'));
 	}
 	free(buf);