MFC r332372-r332374: tail(1)/head(1) compatibility long options

r332372:
tail(1): Add some long options

Add --blocks, --bytes, and --lines long options for -b, -c, and -n
respectively. This improves tail(1)'s compatibility with its GNU counterpart
in a straightforward way.

r332373:
tail(1): Address mandoc concern (space before punctuation after macro)

r332374:
head(1): Provide long options

Provide long options --bytes and --lines to match -c and -n respectively.
This improves head(1)'s compatibility with its GNU counterpart in a sensible
way.