Serialize '--skeleton' generated data in little-endian.

Serialize '--skeleton' generated data in little-endian.

This commit fixes bug #132 "test failure on big endian archs with 0.15.3".

Tests failed because re2c with '--skeleton' option used host endianness
when serializing binary data to file. Expected test result was generated
on little-endian arch, while actual test was run on big-endian arch.

Only three tests failed (out of ~40 tests that are always run with
'--skeleton'), because in most cases data unit is 1 byte and endianness
doesn't matter.

The fix: re2c now converts binary data from host-endian to little-endian
before dumping it to file. Skeleton programs convert data back from
little-endian to host-endian when reading it from file (iff data unit
size is greater than 1 byte).