Patch from Joakim Tjernlund <joakim.tjernlund@lumentis.se>

Here is another update(against BK curr) for crc32(). A kind soul pointed out
the optimizations below.

lib/crc32defs.h:
 - Make it possible to define new values for CRC_LE_BITS/CRC_BE_BITS without
   modifying the source.

lib/crc32.c:
 - Eliminate the need for ENDIAN_SHIFT. Saves a 24 bit shift in the byte
   loops.

 - Swap the XOR expression in DO_CRC. gcc for x86 can not do that simple
   optimization itself(gcc 3.2.2 and RH gcc 2.96 tested). Will improve
   performance with 20-25% on x86.