There is also information on how to reset the stack.

Resolve #2345

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

Fixes #2756.

* Renamed to 'extra-framework-dirs'.
* Added 'extra-framework-dirs' to ConfigFlags.
* Added some checks.
* Updated changelog.

It doesn't make any sense to do a profiling build of an executable if
the library doesn't have a profiled build! The option
--enable-executable-profiling is changed to --enable-profiling to
reflect that it is now a global flag. The old option is still recognized
(for now).

Dynamically linking executables will fail without a shared library
unless the executables do not depend on the library or there is no
library. If there is no library, building shared libraries comes at no
cost. If there is a library, the executables usually depend on it, so it
makes sense to --enable-shared.

If the user passes --disable-shared, it will still be honored, but a
warning will be produced.

path templates.

CompilerInfo contains more information about the compiler than
CompilerId, which just stores the flavour and version. In particular,
CompilerInfo knows an AbiTag, which can be used to tell binary
incompatible results from the same compiler apart, and detailed
information about supported languages and extensions.

Some fields in CompilerInfo may be left unknown (Nothing). This can
be used in the future to allow partially resolving configurations
based on supported languages or extensions.

This patch adds the js-sources field, for JavaScript source code
that should be included in compiled programs, similar to c-sources
for other targets.

It also adds ghcjs-options, ghcjs-shared-options and ghcjs-prof-options
and makes the underlying code for options easier to extend.

Fixes #2130.

While reading the docs, I saw a few typos, so I ran ispell through the
docs. Fixed:

- plain typos
- a few instances of 'ie'→'i.e.' and 'eg' → 'e.g.' for nicer style
- a few capitalisation issues (linux, unix)
- a few not-nice (IMHO) abbreviations (for a manual, that is):
  distro→distribution, repo→repository
- proper naming (RedHat→Red Hat)

Fixes #1403.

The user guide really could really use an overhaul...

This reverts commit 6bfb5a20.

The sandbox feature is already documented (see #1430).
Additionally, the documentation added in this commit is misleading:
'runhaskell Setup.hs sandbox CMD' doesn't work.

See jgm/pandoc#976.

The docs/website sorely need to be reworked, but this will do for now.