dynamically map Python str flags to C enum flags

[avg-I]

Rather than doing this:

for flag in flags:
    c_flag = {
        'embedded_data':    _lib.LZC_SEND_FLAG_EMBED_DATA,
        'large_blocks':     _lib.LZC_SEND_FLAG_LARGE_BLOCK,
    }.get(flag)
    ...

we can algorithmically map the original strings to string corresponding to enum names in the C code and then use getattr(_lib, ...) to obtain actual values.