4.9.4

• Fix crash on some platforms/compilers from invalid garbage reads of varargs
  end marker being an int instead of a nullptr.
• Don't force Windows path separators for GCC when on Windows. As it confuses
  Cygwin GCC's relative include path handling.
  -- René Ferdinand Rivera Morell
• Added common-requirements to project declaration to shorthand as declaring
  the same for both requirements and usage-requirements.
  -- René Ferdinand Rivera Morell
• Add to pass in targets to project explicit rule to reduce duplication of
  explicit targets when there are many.
  -- René Ferdinand Rivera Morell
• Make coverage feature non-incidental and link-incompatible.
  -- Thomas Brown
• Use PATH-based lookup for sh. For things such as Gentoo Prefix, we want to
  use the Bourne shell from the prefix and not the potentially ancient version
  from the main system.
  -- David Seifert