Cleaned -Wunused-variable and -Wunused-local-typedefs warnings for a cleaner build experience

For the sake of a beginner project, cleaned ALL compiler warnings of above types. Defined but unused variables were causing thousands of warnings generated during the build process which flooded the shell screen. The build now runs smoother and looks prettier than before (with all those colors!). There are other warning types still left untouched but they're a lot less in comparison to these. Leaving them alone for now!