Initial commit of libjpeg-turbo plus readme edits.
Add fast jpgcrush mode

Add the fast mode of jpgcrush where:
- Huffman table optimisation is enabled
- Progressive coding mode is enabled
- New default scans are defined for progressive coding
Update cjpeg usage

Add -revert to the list of displayed options in cjpeg help message
Add mozjpeg defaults to jpegtran application

Make mozjpeg settings the default in the jpegtran application.
Behaviour can be reverted to old default settings using the -revert
command line option
Initial version of scan optimisation

First implementation of scan optimisation as done by jpgcrush. Many
parameters are currently hardcoded which should be changed.
Implementation is missing for monochrome.
Clean up scan optimisation code

Lessen use of hardcoded values in luma search
Clean up scan optimisation code

Remove hard coded values and restructure code.
Add command line parameter to control scan optimisation
Add support for scan optimisation of monochrome pictures
Fix issues with chroma scan optimisation
Resolve mismatch with jpgcrush

Add early termination to search for best Al parameter
Clean up scan optimisation code

Remove code that was casting const to non-const
Add pruning of frequency split selection

Skip passes for frequency splitting if they are unlikely to provide
better results.
Moved related fields from cinfo to master object.
Regroup copying of scan buffers
Reorder scan buffers to match jpgcrush order
Implement pruning of search for best number of refinement layers
Move field
Update jpegtran to match jpgcrush behaviour

Modify jpegtran such as to revert to original file if scan optimisation
brings no compression benefit
Fix condition for comparing with original size
Fix issue with uninitialised variable