[std.manip, ext.manip] Better titles for "Standard"/"Extended" manipulators

[frederick-vs-ja]

It seems a bit misleading that the standard distinguishes some manipulators with words "standard" and "extended", as all of these manipulators are standard library components.

[frederick-vs-ja]

CC @msebor (apologizing if you're not the author of N2071 and N2072)

[jwakely]

Maybe "basic" and "extended"?

Although "extended" isn't very descriptive, extended how? What distinguishes them is that they take extra arguments by reference and read/write to those objects. The basic manipulators only take scalar args by value, and so only modify the state of the stream, not any by-reference args.