Missing header

* Some builds reported missing header

src/misc/coordinate.cxx

@@ -20,6 +20,8 @@
 // along with fldigi.  If not, see <http://www.gnu.org/licenses/>.
 // ----------------------------------------------------------------------------
 
+#include <stdio.h>
+
 #include <math.h>
 #include <string.h>
 #include <stdexcept>