The MINIMAL pragma is captured in the parser using a BooleanFormula.
The constructors (mkBool,mkAnd,mkOr) are smart and try to minimise the
boolean formula as it is constructed.
This discards the original information, making round tripping
Note: there is another version which provides a more API Annotations
friendly version of the MINIMAL pragma, but this requires changes to
haddock, which will cause problems for 7.10.2.