Fix compling error in exercise 8 and solution 8

Solution:
1. Remove misplaced #endif

Exercise:
1. Remove extra #ifndef macro and misplaced #endif
2. Remove implementation of constructor, deconstructor and creator in
the arrowLocator header
3. Add missing headers in arrowLocator.cpp
4. Replace OpenMayaRender.mll with OpenMayaRender.lib in the linker
option.