Regen doc/Makefile.in

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.