MFC r349230, r349234, r349477

r349230:
Add a VOP_BMAP(9) man page

Reviewed by: mckusick
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20704

r349234:
VOP_BMAP(9): fix typo in the copyright header

Reported by: rgrimes
MFC-With: 349230
Sponsored by: The FreeBSD Foundation

r349477:
[skip ci] VOP_BMAP.9: fix diction in copyright header

MFC-With: r349230
Sponsored by: The FreeBSD Foundation