Rewrote the opening paragraph of the chapter, added examples on interactions between data and execution policy controls.

In first paragraph, tried to more clearly enumerate and explain the 3 cases.
Added hStreams as an example.  That's not yet published, but will be in a few weeks.

Descibed some interactions between data and execution policy controls, based on some SIMD examples.
 That needs further refinement, in my next round of edits.

Plan to work C++ and Fortran discussion into the research plan section in my next edit.