Changelog for ghc-source-gen-0.2

Changelog for haskell-syntax

Improve overall documentation..
Move patBind to a new HasPatBind class so that it can be used with let' and while'.
Remove GHC.SourceGen.Syntax and export types from relevant modules (for example, HsType' from GHC.SourceGen.Type).
Refactor the treatment of names:
- Rename the constructors of RdrNameStr.
- Make some combinators take OccNameStr instead of RdrNameStr, and introduce the BVar class for patterns.
- Add Eq and Ord instances.
Support more kinds of syntax:
- Deriving clauses
- Import/export lists
- Record expressions and patterns
- Type family instances
- Pattern synonyms (currently, only the prefix form)
Refactor the names and types of match and related combinators, optimizing for the common case of a single expression on the RHS.
Fix edge cases when parsing qualified operators.
Add parentheses in some cases that were previously missing them.
Make ==> have the same precedence as --> to make it easier to combine them.
Make tyApp's precedence match -XTypeApplications.
Fix pretty-printing of rational literals.
Make tyPromotedVar pretty-print as 'Abc not Abc.
Add conP_ for pattern constructors with no arguments.

Initial version.