For cross compiling to targets that don't want to build a compiler

Should fix the windows bots

Add Brian Leibig to AUTHORS.txt for REPL contributions

This reverts commit 2cf6bf87.

Per issue #2418.

Add an optional --logfile argument to std::test::test_main and to
compiletest.

Use this features and the new 'check-summary.py' script to
summarise all the tests performed by the 'check' target. This is
a short term fix for #2075.

Closes #2048

Oops. We can't do this yet until the next snapshot.

Closes #2042
Closes #1981

Begin shift over to using pandoc, markdown and llnextgen for reference manual. Fix man page URL while at it.

We have a bunch of these in the repository.

Doing this is just resulting in a broken workspace. We have a clean-llvm
target that does the right thing. If we want to we can make it a dependency
of clean, but most people don't need to clean llvm and doing so results
in a lengthy rebuild.

Also updated build to install versioned libraries and added a few
missing actions for `make clean`.

Closes #992