v1.1.8: Improvements to adaptive text mode and quicker processing of random data

1. Check for too many uniques to yield compression after initial loops complete and label the return random data.
2. Added check for high bit clear in text mode and output 7-bit non-predefined values when all values have a 0 in high bit.
3. Added definition of predefined characters for adaptive text mode for XML and C data to take advantage of fewer bits for more frequently occurring characters.