Set flags for Intel compiler to prevent incorrect optimization of
arithmetic expressions #826.  Guard against nans in sincosdx #834.
Issue #831 is not addressed here (need more information...).

This attempts to address the geodtest failures noted in #819.
@sebastic can you re-run your tests?

    
Now all of geodesic.c is covered except for 3 lines (and 2 of these are
intentionally dead code).
    
This corresponds to tag v1.49.2-c in the GeographicLib code base.

While testing polygons which encircle the globe multiple times, I
uncovered a problem where the range of the area was not reduced to the
allowed range (either [0, area0) or (-area0/2, area0/2]) correctly.
Since the documentation explicity restricted the calculation of polygon
areas to simple polygons, we'll defer fixing this for now.  (However the
intention was always to handle the area "algebraically" so that, for
example, a "bowtie" has zero area.  So I will plan on fixing this for
1.50.)

Update copyright dates + NEWS.

Implement Polygon AddEdge fix in C library (will be version 1.49.2 of C
library for proj 5.0.0).

Still to do: add tests to expand code coverage.  This will only affect
geodtest.c which is not part of the compiled library.

in GeographicLib). Details:

Workaround bugs in handling of -0.0 in fmod and sin in Visual Studio 10,
11, and 12.

Relax unrealistically strict delta for GeodSolve59 in geodtest.