Fix get_line_alloc()

Assigning the result of getc() to a char makes comparing it to EOF
unreliable, at the very least. You're never too old to make newbie
mistakes.

Thanks to Sebastian Gottschall  for spotting this.

src/util.c

@@ -1041,7 +1041,7 @@ void free_real(const char *func, unsigned int line, void *ptr)
    EOF reached and we return zero. */
 int get_line_alloc(FILE *f, char **buffp, size_t *sizep)
 {
-  char c;
+  int c;
   size_t cnt = 0;
   char *buff = *buffp;