Fixed linker issue when having the linalgebra_util.h header included in more than one file.

Description and explanation of the issue http://stackoverflow.com/questions/14855915/creating-global-variables-causes-linker-error
Added the TOP_SetRawElement() method with inclusion guards with ID "_ROS_DFA_TOOL"

This method is need by the DFA tool to set the Topology vector which is a "private" variable in the C code of the topology.