Fixes <https://bugs.gnu.org/48963>.
Reported by Julien Lepiller <julien@lepiller.eu>.

This reduces peak memory consumption to something less unreasonable.

* Makefile.am (make-go): Depend on 'make-*-go' targets; remove body.
(guile-compilation-rule): New function.
(MODULES_CORE, MODULES_PACKAGES, MODULES_SYSTEM, MODULES_CLI): New
variables.
<top level>: Call 'guile-compilation-rule' 4 times.
* build-aux/compile-all.scm <top level>: Expect "--total" and
"--processed".  Take them into account when displaying progress
reports.

* build-aux/compile-all.scm <top level>: Remove Guile 2.2 workaround.

Works around <https://bugs.gnu.org/40522>.

* build-aux/compile-all.scm (parallel-job-count*): New procedure.
<top level>: Use it instead of 'parallel-job-count'.

* build-aux/compile-all.scm: Wrap 'compile-files' call in 'catch'.
Attempt to resort to 'report-load-error' in (guix ui) to print the
error.

* build-aux/compile-all.scm (%): New procedure.
(command-line): Use it to report completion.

* build-aux/compile-all.scm <top level>: Add calls to 'force-output'
in the #:report-load and #:report-compilation procedures.  Fixes a
regression introduced in 2890ad332fcdfd4bc92b127d783975437c8b718b
whereby compilation output would be buffered, leading to a weird
visual effect.

* build-aux/compile-all.scm (parallel-job-count): New procedure.
<top level>: Pass it to 'compile-files' as #:workers.

* guix/build/compile.scm: New file.
* Makefile.am (MODULES): Add it.
* build-aux/compile-all.scm: Use it.
(warnings, file->module, load-module-file)
(%default-optimizations, %lightweight-optimizations)
(optimization-options, compile-file*): Remove.
<top level>: Use 'compile-files'.
* guix/build/pull.scm (%default-optimizations)
(%lightweight-optimizations, optimization-options): Remove.
(build-guix): Rewrite as a call to 'compile-files'.
* guix/discovery.scm (file-name->module-name): Export.

* build-aux/compile-all.scm (warnings): Add 'macro-use-before-definition'.

This avoids collisions with '_' when the latter is used as a 'match'
pattern for instance.  See
<https://lists.gnu.org/archive/html/guix-devel/2017-04/msg00464.html>.

* guix/ui.scm: Rename '_' to 'G_'.
* po/guix/Makevars (XGETTEXT_OPTIONS): Adjust accordingly.
* build-aux/compile-all.scm (warnings): Remove 'format'.
* gnu/packages.scm,
gnu/services.scm,
gnu/services/shepherd.scm,
gnu/system.scm,
gnu/system/shadow.scm,
guix/gnupg.scm,
guix/http-client.scm,
guix/import/cpan.scm,
guix/import/elpa.scm,
guix/import/pypi.scm,
guix/nar.scm,
guix/scripts.scm,
guix/scripts/archive.scm,
guix/scripts/authenticate.scm,
guix/scripts/build.scm,
guix/scripts/challenge.scm,
guix/scripts/container.scm,
guix/scripts/container/exec.scm,
guix/scripts/copy.scm,
guix/scripts/download.scm,
guix/scripts/edit.scm,
guix/scripts/environment.scm,
guix/scripts/gc.scm,
guix/scripts/graph.scm,
guix/scripts/hash.scm,
guix/scripts/import.scm,
guix/scripts/import/cpan.scm,
guix/scripts/import/cran.scm,
guix/scripts/import/crate.scm,
guix/scripts/import/elpa.scm,
guix/scripts/import/gem.scm,
guix/scripts/import/gnu.scm,
guix/scripts/import/hackage.scm,
guix/scripts/import/nix.scm,
guix/scripts/import/pypi.scm,
guix/scripts/import/stackage.scm,
guix/scripts/lint.scm,
guix/scripts/offload.scm,
guix/scripts/pack.scm,
guix/scripts/package.scm,
guix/scripts/perform-download.scm,
guix/scripts/publish.scm,
guix/scripts/pull.scm,
guix/scripts/refresh.scm,
guix/scripts/size.scm,
guix/scripts/substitute.scm,
guix/scripts/system.scm,
guix/ssh.scm,
guix/upstream.scm: Use 'G_' instead of '_'.  Most of this change was
obtained by running: "sed -i -e's/(_ "/(G_ "/g' `find -name \*.scm`".