Use the proper markup for single quotes.
Use the same 6000 series g2{a,b} firmware versions when embedding these
images into the kernel as currently included into iwn6000g2{a,b}fw.ko
and delete the old files, missed in r254199 and r259135 respectively.

MFC after:	3 days
Bump .Dd for change done in r275908
Const'ify a firmware image missed in r251142.

MFC after:	3 days
Convert the BSC (i2c) driver to use the new iicbus_get_frequency().

Tested on:	Raspberry pi
Fix a off-by-one bug.

Pointy hat to:	loos
Remove unnecessary code and, instead, use the provided iicbus_null_callback
callback.
Add LIBADD to PROG_VARS, similar to DPADD/LDADD
Build/install lib/libc/tests/hash/t_sha2 if MK_OPENSSL == yes

Reported by: Beeblebrox <zaphod@berentweb.com>
Fix the function signatures when MK_CRYPT == no for snmp_get_local_keys and
snmp_passwd_to_keys

MFC after: 1 week
Reported by: Beeblebrox <zaphod@berentweb.com>
Parallelize building lib/ncurses

MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D1353
Improve/fix interrupt allocation/setup/release:
- Simplify MSI allocation to what is actually needed for a single one.
- Release the MSI and the corresponding bus resource as appropriate when
  either the interrupt resource cannot be allocated or setting up the
  interrupt fails.
- Error out when interrupt allocation or setup fails and polling is
  disabled.
- Release the MSI after the corresponding bus resource so the former is
  not leaked on detach.
- Remove a redundant softc member.

MFC after:	3 days