Fixing documentation.

Change-Id: I37dc28841fb991769543e3749aeba0f83c420a74
More documentation updates.

Change-Id: I6869fef6042d5249be98c3c0c3337491936276c1
Fixed a bug in reading vtu data with polyhedron cells

Paraview bug: http://www.paraview.org/Bug/view.php?id=13892
If there are polydhedron cells in multiple pieces of a vtu file, the
vtkXMLUnstructuredDataReader will fail to read properly the polyhedron
cell and faces info, except the cell in first piece. The bug is in the
logic of figuring out the offset of faces and points when there are
multiple pieces containing polyhedron cells.

Change-Id: Ic1100bc816c1e0f51cc45bc34d26ec92799bd36f
Added a test for XMLUnstructuredGridReader

Change-Id: I8ebd896d483684cac7df4d7313f4fa8541437ab3
ENH: Improve finding of isnan and friends.

These functions can be defined in various ways:
1) in C++11 as std::isinf(), std::isnan(), std::isfinite() in <cmath>
2) in C99 as isinf(), isnan(), isfinite() in <math.h>
3) in pre-C99 extensions as isinf(), isnan(), finite() in <math.h>
4) on Windows as _isinf(), _finite() in <float.h>

Change-Id: I5817f43eb167c26bdfe6521ce5376262ba71b600
Merge topic 'better-math-function-finding' into master

17c5a4e8 ENH: Improve finding of isnan and friends.
Merge topic 'polyhedron_pieces_in_vtu' into master

cd39d68b Added a test for XMLUnstructuredGridReader
8bc56514 Fixed a bug in reading vtu data with polyhedron cells
Merge topic 'documentation_updates' into master

1a6a08d4 More documentation updates.
28c97ad8 Fixing documentation.