- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

Use const instead of __const, and merge the license change from NetBSD.

Obtained from: NetBSD

Teach fmtcheck() about wint_t, intmax_t, char *, intmax_t *, and
wide string arguments.

Also simplify the code that handles length modifiers and make it
more conservative. For instance, be explicit about the modifiers
allowed for %d, rather than assuming that anything other than L,
q, t, or z implies an int argument.

Teach fmtcheck() about the ' (thousands separator) flag.

When *printf() and *scanf() are compiled without floating-point
support, fmtcheck() should not accept format strings that contain
floating-point formats.

Teach fmtcheck(3) about the flags a, A, F, G, t, and z.

Remove improper use of <namespace.h>.
Remove fmtcheck from application name space (fix the weak reference).

Fix SCM ID's.

Removed duplicate VCS ID tags, as per style(9).

Remove unnecessary #include <stdlib.h>

Obtained from: NetBSD
MFC After: 1 week

Add fmtcheck(), a function for checking consistency of format string
arguments where the format string is obtained from user data, or
otherwise difficult to verify statically.

Example usage:

printf(fmtcheck(user_format, standard_format), arg1, arg2);

checks the format string user_format for consistency (same number/order/
type of format operators) with standard_format. If they differ,
standard_format is used instead to avoid potential crashes or security
violations.

Obtained from: NetBSD
Reviewed by: -arch