More GNU/Linux C++ compilation tips

As detailed in the Header dependency streamlining, originally found here, many of the standard C++ library include files have been edited to only include the smallest possible number of additional files. As such, many C++ programs written without including <cstdlib> will no longer compile.

If you receive: error: ‘strtoul’ was not declared in this scope

Fix it by including: #include <stdlib.h> in the offending source file.