Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Make the PAM password strength checking module WARNS=2 safe.

lib/libpam/modules/pam_passwdqc/Makefile:
Bump WARNS to 2.

contrib/pam_modules/pam_passwdqc/pam_passwdqc.c:
Bump _XOPEN_SOURCE and _XOPEN_VERSION from 500 to 600
so that vsnprint() is declared.

Use the two new union types (pam_conv_item_t and
pam_text_item_t) to resolve strict aliasing violations
caused by casts to comply with the pam_get_item() API taking
a "const void **" for all item types. Warnings are
generated for casts that create "type puns" (pointers of
conflicting sized types that are set to access the same
memory location) since these pointers may be used in ways
that violate C's strict aliasing rules. Casts to a new
type must be performed through a union in order to be
compliant, and access must be performed through only one
of the union's data types during the lifetime of the union
instance. Handle strict-aliasing warnings through pointer
assignments, which drastically simplifies this change.

Correct a CLANG "printf-like function with more arguments
than format" error.

Submitted by: gibbs
Sponsored by: Spectra Logic

This commit was generated by cvs2svn to compensate for changes in r94889,
which included commits to RCS files with non-trunk default branches.

Vendor import of pam_passwdqc v0.5.

Bug & warning fixes; pretty much what will become 0.5 later this week.

Submitted by: Solar Designer <solar@openwall.com>

Vendor import of Solar Designer's pam_passwdqc module.