Fix #3041, ifndef all CURRENT_PACKAGE_KEY and related macros.

I also realized LOCAL_COMPONENT_ID is pessimal if we don't
depend on a library, so I removed it. (It has never been
in a real Cabal release.)

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Fix #3483, set HASKELL_DIST_DIR

Clarify what logical negation of impl with version ranges means

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

See https://ghc.haskell.org/trac/ghc/ticket/12494;

 we cargo-culted
some incorrect code from base. Lift the restriction.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Fix preprocessors to put output in correct directory.

[ci skip]

Add new 'autogen-modules' field. This closes #3656 and  #719

Modules that are built automatically at setup, like Paths_PACKAGENAME or others created with a build-type custom, appear on 'other-modules' for the Library, Executable, Test-Suite or Benchmark stanzas or also on 'exposed-modules' for libraries but are not really on the package when distributed. This makes commands like sdist fail because the file is not found, so with this new field modules that appear there are treated the same way as Paths_PACKAGENAME was and there is no need to create complex build hooks.
Just add the module names on 'other-modules' and 'exposed-modules' as always and on the new 'autogen-modules' besides.

Rework new-build failure reporting to include build logs

Revert "Fix getExecutablePath on *BSD."

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Make annotateFailure take a maybe log file, and add a
annotateFailureNoLog for the other case. This is a little more future
proof and simplifies things at the call sites.

AppVeyor fails installing GHC 7.10.3

This fixes #3687

Swithed AppVeyor test to GHC 8.0.1 because 7.10.3 is broken (https://chocolatey.org/packages/ghc/7.10.3) and added the `-y` option and `refreshenv` after installing GHC as suggested by Chocolatey

Reporting build logs is important as we otherwise have no real info for
why deps failed to build. It does make the presentation more difficult
however because build logs can be long and in principle there can be
several, which means it can take up more than a single screen in a
console. The first thing users notice is typically the last few
messages, so in the case that we're presenting long build logs then its
important to also include a short summary at the end.

So our approach is this: for packages where we want to show a build log,
we dump those first, in full, each with a header to indicate which
package it is, log file name (for later reference), plus any extra
detail we have from the phase of the failure or the exception. Then
after all build logs we end with a short summary of the failure(s). For
packages where we do not show a build log (e.g. local packages that dump
live to the console) we only present a summary at the end, but we
include a little more detail than for the packages that had a build log
since this is the only thing we report for them. So we include details
of the exception.

The PlanningFailed case does not happen. The ReplFailed, HaddocksFailed
cases were previously covered by BuildFailed but they're worth
disinguishing.

In both cases it's optional and only added when the log file is used.
This will be used later in reporting the build outcomes.

We're going to alter and extend the BuildResult and BuildFailure types
for the new-build code, so we cannot share those types with the old
install code.

This patch doesn't change the structure, just redefines them locally and
switches uses to record style so we can add new fields easily.

I think these names are now a bit more induitive / less confusing and a
bit more consistent.

We now have BuildOutcome(s) to mean either failure or a build result,
and BuildResult to mean the result of a non-failing build.

Solver: Only link packages to other unlinked packages.

Fix #3676, don't use --branch when checking out a branch with Git.

Make registration less chatty.

Solver: Use difference lists to combine logs in 'Explore.exploreLog'.

[ci skip]

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>