Add abs functions for imag(32) and imag(64) and a test that uses them

[Reviewed by Brad]

These return reals with the same bit size as their inputs. They convert their
input to real using the internal _i2r() functions, then call the real abs()
functions.  Added the two new functions to the Standard Modules section of the
spec.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@22105 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Making the MassiveThreads clean rule a bit more like other third-party packages




git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@22106 3a8e244f-b0f2-452b-bcba-4c88e055c3ca
Fixed up the return types of methods like add() in the internal Atomics.chpl module.

[reviewed by Tom]

In Atomics.chpl a bunch of methods like add() claim non-void return types
while not returning anything. A bug future for compiler not reporting
an error is already filed (r22103, r22104).

I specified :void return type explicitly (as opposed to leaving that
implicit, like the write(...) methods do) by Tom's request.


git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@22107 3a8e244f-b0f2-452b-bcba-4c88e055c3ca