#1 patch for compiling under Ubuntu g++ 4.4.3

[Lars Huttar]

Hi ... enjoying hyperart -- the paper, the app, and the source code. Thanks for making it open source.

These patches add several "#include" statements that I found necessary to get hyperart to compile under Ubuntu / g++ 4.4.3.
I also changed abs() to labs() in datareader.cpp, to make g++ happy.

(There are also a lot of warnings like "element.h:32: warning: type qualifiers ignored on function return type", which I'm ignoring.)

[Lars Huttar]

add several "#include" statements that I found necessary to get hyperart to compile under Ubuntu / g++ 4.4.3.