Cabal documentation

[Henning Thielemann]

I have added some suggestions about conditional compilation to
    https://www.haskell.org/haskellwiki/Cabal/FAQ#Conditional_compilation

Maybe my suggestion about using Hs-Source-Dirs for conditional compilation 
can be added to
    http://www.haskell.org/cabal/release/cabal-latest/doc/users-guide/authors.html#cpp


I'm confused with a paragraph from
   http://www.haskell.org/ghc/docs/latest/html/Cabal/authors.html

"If dependencies were missing, the last flag (as by the order in which 
the flags were introduced in the package description) is tried with its 
alternative value and so on. This continues until either an assignment is 
found where all dependencies can be satisfied, or all possible flag 
assignments have been tried."

I assumed that the automatic search for appropriate flag assignments is 
only done by cabal-install, not by Cabal.