libc: Implement N2630.

This adds formatted input/output of binary integer numbers to the printf(), scanf(), and strtol() families, including their wide-character counterparts.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41511

(cherry picked from commit d9dc1603d6e48cca84cad3ebe859129131b8387c)

libc: Add unit tests for N2630 and possible collateral damage.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41512

(cherry picked from commit b9385720f34b536ef2568a642e8b1fad0450056f)

libc: Document support for binary integers.

Reviewed by: debdrup, emaste
Differential Revision: https://reviews.freebsd.org/D41522

(cherry picked from commit 76edfabbecdec686a570b8e009d5ea4112f943e0)

libc: Fix fixed-width case in the new integer parser.

Fixes: d9dc1603d6e4
Differential Revision: https://reviews.freebsd.org/D41622

(cherry picked from commit aca3bd1602577591e5cd237c4bb0bb71b3be0c75)

libc: Add a wide version of snprintf_test.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41726

(cherry picked from commit 4ec9ee9912765ac4ca57353999caa92a23283d8e)

libc: Suppress format checks on printf() / scanf() tests.

Reviewed by: jrtc27, markj, emaste
Differential Revision: https://reviews.freebsd.org/D41727

(cherry picked from commit 294bd2827e61a78041f6613f4b82235fcc454157)

Approved by: re (gjb)