re PR pch/10757 (Adding -fpic/-fPIC causes crash with PCH created without -fpic/...

re PR pch/10757 (Adding -fpic/-fPIC causes crash with PCH created without -fpic/-fPIC)

	PR 10757
	* c-pch.c: Include target.h.  Improve comments.
	(struct c_pch_validity): Add target_data_length.
	(pch_init): Add target's validity data.
	(c_common_valid_pch): Check target's validity data.
	* target-def.h (TARGET_GET_PCH_VALIDITY): New.
	(TARGET_PCH_VALID_P): New.
	(TARGET_INITIALIZER): Add new fields.
	* target.h: Include tm.h.
	(struct gcc_target): Add get_pch_validity, pch_valid_p.
	* toplev.h (default_get_pch_validity): New prototype.
	(default_pch_valid_p): New prototype.
	* toplev.c (default_get_pch_validity): New routine.
	(default_pch_valid_p): New routine.
	* Makefile.in (TARGET_H): Add TM_H.  Replace all users of
	target.h with $(TARGET_H).
	(c-pch.o): Add TARGET_H.
	* doc/tm.texi (PCH Target): New node.
	(TARGET_GET_PCH_VALIDITY): Document.
	(TARGET_PCH_VALID_P): Document.

From-SVN: r72909