Also make the automake strictness "foreign". My regeneration of the
three doc/Makefile.in files already had --foreign in the automake
invocation, so this just makes it explicit.
bfd/
* doc/Makefile.am (AUTOMAKE_OPTIONS): Add "foreign".
* doc/Makefile.in: Regenerate.
binutils/
* doc/Makefile.am (AUTOMAKE_OPTIONS): Add "foreign".
* doc/Makefile.in: Regenerate.
gas/
* doc/Makefile.am (AUTOMAKE_OPTIONS): Add "foreign".
* doc/Makefile.in: Regenerate.
zlib/
* Makefile.in: Regenerate.
* configure.ac: Restore old behaviour of only enabling multilibs
when a target subdirectory is defined. This allows building with
srcdir == builddir.
* configure: Regenerate.