Export CatchInfo,CatchInfoOnce constructors of Handler

This fixes warnings following
    commit 910a642294eb3547d0cbb3d5735ad81b964f137b
    Author: Simon Peyton Jones <simonpj@microsoft.com>
    Date:   Mon Oct 29 23:25:25 2012 +0000
    Do not treat a constructor in a *pattern* as a *use* of that constructor

I'm not sure if this is the right thing to do: In
    commit 1c4608e3b8737dbb9204f850af4d680ccea7d8ec
    Author: Simon Marlow <marlowsd@gmail.com>
    Date:   Thu Feb 19 10:05:32 2009 +0000
    Rewrite of signal-handling.
the commit message says:
    The new implementation has the capability to define signal handlers
    that have access to the siginfo of the signal (#592), but this
    functionality is not exposed in this patch.
but this at least gets validate builds working again, and we can change
it if necessary as part of #2451
Add comment to .cabal file saying what GHC 7.6.1 shipped with
Bump version number following new policy

We now keep the HEAD version numbers as values which would be suitable
for immediate release.
Update dependencies
Bump base lower version to 4.5 (the version GHC 7.4.1 came with)

and remove code to support older versions
Fix putenv; trac #7342

We were freeing the string, but the string becomes part of the
environment.
execvpe exists on QNX
Fix some parentheses

I assume that this is what was intended.
Use pthread_kill on OS X too

Fixes signals004(threaded1,threaded2) on OS X 32.
Rename tests to not start with a digit
Import waitpid() with interruptible
Indicate whether a process dumped core in the ProcessStatus

The Bool field of Terminated is new, as is the documentation:

data ProcessStatus
   = Exited ExitCode        -- ^ the process exited by calling
                            -- @exit()@ or returning from @main@
   | Terminated Signal Bool -- ^ the process was terminated by a
                            -- signal, the @Bool@ is @True@ if a core
                            -- dump was produced
   | Stopped Signal         -- ^ the process was stopped by a signal
   deriving (Eq, Ord, Show)

This is an API change, hence will need a major version bump.
change notes
cope with missing pw_gecos (for Android)

Submitted by: Nathan Hüsken <nathan.huesken@posteo.de>
cope with missing telldir/seekdir (for Android)

Submitted by: Nathan Hüsken <nathan.huesken@posteo.de>
Terminated has an extra field now
Follow changes in the testsuite
Don't bother marking unix tests as 'skip' on Windows

We don't run the unix tests on Windows anyway.
Small testsuite refactoring; no functional change
Remove uses of compose(s) in tests