Fun bug: haddock eats the last character of the text inside a hyperlink.

--HG--
rename : changelog => changelog.md

Allow gunfold

Remove redundant 'const' qualifiers.

This makes the cabal constraint solver's job easier (fewer
combinations to try) and makes it impossible for it to set developer
to True when installing the library.

Replace the old text smart constructor with the slightly smarter
one we've had all along that ensures that it doesn't pin its array
if it's empty.