[Fix] Fix buffer overflow when printing small floats

contrib/fpconv/fpconv.h

  *
  */
 
-int fpconv_dtoa(double fp, char dest[24], bool scientific);
+int fpconv_dtoa(double fp, char dest[32], bool scientific);
 
 #endif
 

src/libutil/printf.c

 	const gchar *fmt,
 	va_list args)
 {
-	gchar zero, numbuf[G_ASCII_DTOSTR_BUF_SIZE], dtoabuf[24], *p, *last, c;
+	gchar zero, numbuf[G_ASCII_DTOSTR_BUF_SIZE], dtoabuf[32], *p, *last, c;
 	const gchar *buf_start = fmt, *fmt_start = NULL;
 	gint d;
 	gdouble f;