HPCC-12029 Optimize crc_file, updated to fix Centos 5.7 and OSX build er...

re-opened and new commit to fix Centos 5.7 and OSX build issues.

Signed-off-by: Mark Kelly <mark.kelly@lexisnexis.com>
ok, so something like this -
    uint32_t crcs = crc;
    _REV4(crcs);
    uint32_t one = *current++ ^ crcs;

instead of -
    uint32_t one = *current++ ^ swap_bytes(crc);

or I could change swap_bytes to use _REV4() when not builtin.