Introduce generic _F1_CHECK_EXP(), which is like the macros for checking
values (_F1_EQ_CHECK_INT() etc). Reuse the same for introducing
_F1_EQ_CHECK_OPTIONAL_IE that will be used to write the check for
optional fields more concisely.
CP_OPT_BYTE_ARRAY() FREE_OPT_BYTE_ARRAY() are macros to wrap handling of
optional byte arrays.
_F1_MALLOC() simplifies allocations and is similar to asn1cCallocOne(),
but provided to avoid confusion (since more than ASN.1 structures will
use it).
All will be used in the following commits.