Support for Java 9 Flow API

[fvasco]

Rename kotlinx-coroutines-reactive package to Java 9 package.

[elizarov]

Why rename? kotlinx-coroutines-reactive support Reactive Streams specification interfaces. It does not work with Java 8 Flow.* interfaces. We should define a new module for that. The only tricking part is how name it: either kotlinx-coroutines-jdk9 or kotlinx-coroutines-flow.

[fvasco]

Hi @elizarov,
I said that badly, I am fully agree with you.

Both names are nice,
I consider a bit better to offer a complete jdk 9 integration as a single dependency, however this goal can be reached by putting kotlinx-coroutines-flow as dependency of kotlinx-coroutines-jdk9.

[elizarov]

What else there is to jdk 9 integration beyond Flow.* interfaces?

[fvasco]

Nothing,
so I prefer the name kotlinx-coroutines-jdk9.

Flow api should not look different from time api.

[qwwdfsad]

Fixed in 1.3.5