Update configure.ac
Update configure.ac

fixing problem found when using autoreconf-2.69
mojmir-svoboda/asn1c,mojmir-svoboda/asn1c,xxkkk/asn1c,xxkkk/asn1c,khmseu/asn1c,khmseu/asn1c,mojmir-svoboda/asn1c,mouse07410/asn1c,xxkkk/asn1c,khmseu/asn1c,mouse07410/asn1c,hongyunnchen/asn1c,xxkkk/asn1c,khmseu/asn1c,mouse07410/asn1c,hongyunnchen/asn1c,hongyunnchen/asn1c,mouse07410/asn1c,hongyunnchen/asn1c,mojmir-svoboda/asn1c