* cipher/ecc-curves.c (gcry_ecc_get_curve): Handle G, differently.
* cipher/ecc-misc.c (_gcry_ecc_sec_decodepoint): Support compressed
representation of EC point.  Rename from _gcry_ecc_os2ec.
* cipher/ecc-sm2.c (_gcry_ecc_sm2_decrypt) Follow the change.
* cipher/ecc.c (ecc_decrypt_raw): Likewise.
* mpi/ec.c (_gcry_mpi_ec_set_point): Likewise.
* src/ec-context.h: API change _gcry_ecc_sec_decodepoint from
_gcry_ecc_os2ec.
* tests/basic.c (check_pubkey): Use compressed representation
for two public keys of NIST P192 and NIST P256.