ANN: Paraffin 4.2, Parallelism Generics

[Brad Moore <brad.moore@shaw.ca>]

This is a minor update to the Paraffin release 4.1 that was released a 
couple days ago.

This release (4.2) is geared towards getting the Ravenscar version of 
the FFT (Fast Fourier Transform) paraffinalia app to work on Windows, 
and other targets where synchronous barriers are implemented by
protected types.

To achieve this, a new package, called 
Parallel.Simple_Synchronous_Barriers was introduced.

This package provides the services of a barrier when only two tasks
need to wait on the barrier, and is implemented using Ada's suspension
objects, rather than a protected type.

The issue is that on Windows, Ada.Synchronous_Barriers is implemented
by a protected object in GNAT. Ravenscar disallows protected objects
to be declared at a nested level, which is needed by the FFT app.
Since only two tasks ever need to wait on a barrier in the FFT
algorithm, a specialized implementation of a barrier can be constructed
using Ada's suspension objects.

This specialized barrier satisfies the Ravenscar restrictions, but also
is lighter weight, and was deemed worthwhile for use for the 
non-ravenscar version of fft.

As a result of this change, the project file test_ravenscar_fft_linux
was renamed to test_ravenscar_fft, since it should now be portable to
all targets.

The latest stable release and older releases may be downloaded from;

  https://sourceforge.net/projects/paraffin/files/

For those who want the current development versions of the source they
can download using git (http://git-scm.com/) by issuing the following
commands;

  mkdir sandbox
  cd sandbox
  git clone git://git.code.sf.net/p/paraffin/code paraffin-code