Include <strings.h> for strncasecmp() declaration [minor]

Author: jmarshall

convert.c

@@ -28,6 +28,7 @@ THE SOFTWARE.  */
 #include <assert.h>
 #include <ctype.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <sys/stat.h>
 #include <sys/types.h>