mpi: Fix scanning of negative SSH formats and add more tests.
* mpi/mpicoder.c (gcry_mpi_scan): Fix sign setting for SSH format. * tests/t-convert.c (negative_zero): Test all formats. (check_formats): Add tests for PGP and scan tests for SSH and USG. * src/gcrypt.h.in (mpi_is_neg): Fix macro. * mpi/mpi-scan.c (_gcry_mpi_getbyte, _gcry_mpi_putbyte): Comment out these unused functions.
- Signed-off-by: Werner Koch <wk@gnupg.org>