Increase buffer size for thousands processing

E.g. yue does not have many thousands separators, so the value may be very
large, possibly as much as maxint.

src/libespeak-ng/numbers.c

 	// thousands_exact:  bit 0  no hundreds,tens,or units,  bit 1  ordinal numberr
 	int found;
 	int found_value = 0;
-	char string[12];
+	char string[14];
 	char ph_of[12];
 	char ph_thousands[40];
 	char ph_buf[40];