* c-pch.c: Add comments in various places.
(struct c_pch_validity): Add the lengths of various strings.
(host_machine): New static.
(target_machine): New static.
(get_ident): Bump version number.
(pch_init): Write out version, host, target validity data.
(c_common_valid_pch): Check version, host, target.
* Makefile.in (c-pch.o): Add version.h; define HOST_MACHINE and
TARGET_MACHINE.
From-SVN: r72774
