Porpage/Dependency/Types.hs: add missing comparison for strict/nonstrict bounds

Hackport broke on darcs ebuild, which has nonstrict haskeline upper bound:
    >=dev-haskell/haskeline-0.6.3:=[profile?] <=dev-haskell/haskeline-0.6.4.6:=[profile?]

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Merge/Dependencies.hs: suppress partial pattern matching warnings

Properly supporting non-ghc will be a major change.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
tests/normalize_deps.hs: fix commented out test

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Portage/Dependency/Normalize.hs: added rough use-guarded lifting

Now it is able to lift simplest cases like this:
    a? ( b? ( a b ) )
    !a? ( b? ( b c ) )
into
    b? ( b )
    a? ( b? ( a ) )
    !a? ( b? ( c ) )

Very common case for our USE-flag bruteforcer.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>