Added TODOs from IdeSlave.hs
Add syntax for example code to docs

Now, code defined with the "example" Markdown attribute will be rendered
as an inline REPL-style example. For instance:

````idris example
with List (reverse ["a", "b", "c"])
````

renders to

        > reverse ["a", "b", "c"]
        ["c", "b", "a"]
Lifted TODOs and FIXMEs from clause and instance elaborator
Removed old comment from `src/Idris/Elab/Data.hs`
Added TODOs and FIXMEs from the Elaborator for Data.
Lifted the TODOs from Primitives.hs
Merge pull request #1613 from david-christiansen/doc-examples

Add syntax for example code to docs
Factor `addSyntax` out of `syntaxDecl` parser
:let at the REPL now supports syntax extensions!
Merge branch 'master' of https://github.com/idris-lang/Idris-dev into repl-definitions
Solve more implicits before 'case' elaboration

Otherwise we can generate a type for the 'case' block which is not
specific enough, if there are lots of dependencies. Fixes #1620.
Merge branch 'master' of git://github.com/idris-lang/Idris-dev into case-fix
Merge pull request #1618 from jfdm/tidyup/lift-todos-3

More lifting of TODO/FIXMEs from the source.
Merge pull request #1621 from trillioneyes/repl-definitions

Repl definitions
Merge pull request #1622 from edwinb/case-fix

Case fix