Add --enable-host-shared configuration option

Add --enable-host-shared configuration option

/
	* configure.ac: Add --enable-host-shared
	* configure: Regenerate.

gcc/
	* Makefile.in (PICFLAG): New.
	(enable_host_shared): New.
	(INTERNAL_CFLAGS): Use PICFLAG.
	(LIBIBERTY): Use pic build of libiberty.a if configured with
	--enable-host-shared.
	* configure.ac: Add --enable-host-shared, setting up new
	PICFLAG variable.
	* configure: Regenerate.
	* doc/install.texi (--enable-shared): Add note contrasting it
	with...
	(--enable-host-shared): New option.

libbacktrace/
	* configure.ac: Add --enable-host-shared, setting up
	pre-existing PIC_FLAG variable within Makefile.am et al.
	* configure: Regenerate.

libcpp/
	* Makefile.in (PICFLAG): New.
	(ALL_CFLAGS): Add PICFLAG.
	(ALL_CXXFLAGS): Likewise.
	* configure.ac: Add --enable-host-shared, setting up new
	PICFLAG variable.
	* configure: Regenerate.

libdecnumber/
	* Makefile.in (PICFLAG): New.
	(ALL_CFLAGS): Add PICFLAG.
	* configure.ac: Add --enable-host-shared, setting up new
	PICFLAG variable.
	* configure: Regenerate.

libiberty/
	* configure.ac: If --enable-host-shared, use -fPIC.
	* configure: Regenerate.

zlib/
	* configure.ac: Add --enable-host-shared, setting up new
	PICFLAG variable.
	* Makefile.am: Add PICFLAG to libz_a_CFLAGS.
	* Makefile.in: Regenerate.
	* configure: Regenerate.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@203632 138bc75d-0d04-0410-961f-82ee72b054a4