Fix linking of some uniconv tests on FreeBSD.

Fix linking of some uniconv tests on FreeBSD.

* modules/uniconv/u16-conv-from-enc-tests
(test_u16_conv_from_enc_LDADD): Link $(LDADD) before @LIBICONV@.
* modules/uniconv/u16-conv-to-enc-tests
(test_u16_conv_to_enc_LDADD): Likewise.
* modules/uniconv/u16-strconv-from-enc-tests
(test_u16_strconv_from_enc_LDADD): Likewise.
* modules/uniconv/u16-strconv-to-enc-tests
(test_u16_strconv_to_enc_LDADD): Likewise.
* modules/uniconv/u32-conv-from-enc-tests
(test_u32_conv_from_enc_LDADD): Likewise.
* modules/uniconv/u32-conv-to-enc-tests
(test_u32_conv_to_enc_LDADD): Likewise.
* modules/uniconv/u32-strconv-from-enc-tests
(test_u32_strconv_from_enc_LDADD): Likewise.
* modules/uniconv/u32-strconv-to-enc-tests
(test_u32_strconv_to_enc_LDADD): Likewise.
* modules/uniconv/u8-conv-from-enc-tests
(test_u8_conv_from_enc_LDADD): Likewise.
* modules/uniconv/u8-conv-to-enc-tests
(test_u8_conv_to_enc_LDADD): Likewise.
* modules/uniconv/u8-strconv-from-enc-tests
(test_u8_strconv_from_enc_LDADD): Likewise.
* modules/uniconv/u8-strconv-to-enc-tests
(test_u8_strconv_to_enc_LDADD): Likewise.