Added examples, more detailed documentation to Data.List functions of "Extracting sublists" section

[guest]

Goal of my changes it to make list functions more accessible to Haskell newcomers. "Extracting sublists" section seems to have less complete documentation than rest of the module.

Added examples for all the functions. Added easier to understand summaries for composite functions.

[guest]

Proposal deadline: Wednesday, December 6th.

Andriy

[Andriy]

New version of the patch - added examples for corner cases.

[Andriy]

HTML file showing Haddock results for the affected part of documentation.

[Andriy]

No dissent. Supported by Donald Bruce Stewart, Neil Mitchell, Ross Paterson.

Neil Mitchell suggested to include corner cases which I did in the second version of the patch (attached). He later suggested to add QuickCheck? style properties. I decided to leave this out of scope for this proposal.

[igloo]

Patch applied to HEAD and 6.6 branches.