let's deprecate view bounds by default (not just under -Xfuture)

[SethTisue]

scala/scala#2909 deprecated view bounds under -Xfuture, but nobody ever came back and removed the if (settings.future) check in Parsers.scala. as far as I know, that was just an oversight

there is a question of whether this change should target 2.12 or 2.13. I suggest we target 2.12.5 for the deprecation, and then actually remove it from the language in 2.13.

[SethTisue]

someone want to tackle this...?

[SethTisue]

anyone interested in tackling this might also like to tackle the slightly broader scala/scala-dev#471 and other pieces of scala/scala-dev#430

[eed3si9n]

I didn't see a PR yet on this, so I took it.

[SethTisue]

I suggest we target 2.12.5 for the deprecation, and then actually remove it from the language in 2.13.

we went with a slower timetable: deprecated in 2.13, slated for removal in 2.14.