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Print the list of strings that are accepted in a LANGUAGE pragma,
or as a -XFoo flag. (No can be prepended to any of the strings).

-fparr did exist before, it just wasn't documented.

Now we only allow -XFooBar syntax, not alternate case, hyphens or -f.
There are some deprecated -f flags accordingly.

Adaptated from code from Sigbjorn Finne

Fixes read002 on x86_64 (and maybe others).  The stg_ap_f_info info
table had the wrong liveness on it, because the float had been treated
as having zero size.

A Name used to have a Parent, but no longer has.  When we want to 
print info about data type T and data constructor MkT, the info about
T already describes MkT so we want to discard the latter.  Now that
Names don't have a Parent, we must do that in a different way,
using implicitTyThings

Test is ghci011