Missing examples 'opengl' and 'subclass' build support in makefile

[programmingkidx]

The makefile in the root level of the project currently does not support the opengl and subclass examples. I ask that these two example projects be included in the makefile for building and running.

Thank you.

[progrium]

I'm not even sure how much I want to keep those make tasks in there, but you are free to add them. They are similar to the others.