Big endian C codegen - #79

…nter indexing

The encoder's ((unsigned char *)&(field))[fi] pattern accesses bytes via host
memory layout, which gives wrong values on big-endian targets (e.g. TMS570)
because fi=0 maps to the MSB instead of the LSB.

Replace both encoder and decoder items with explicit bit-shift arithmetic that
is endian-neutral:

  Encoder: ((unsigned_type)(chain) >> (fi*8 + shift)) & mask
  Decoder: chain |= (chain_type)(((unsigned)s[si] shift) & mask) << (fi*8))

The decoder always uses |= rather than = so it accumulates bytes without
clobbering already-written ones; a memset(m, 0, sizeof(*m)) at the top of
each generated Decode function provides the required zero baseline.
string.h is included in the generated .c file for optimization mode.

Regenerate C/CPP optimization-mode examples to reflect the new output.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>