Added check_for_libfiles

-Added check_for_libfiles: checks if SDL2 and support packages are
installed; if not, check if they were downloaded and do the work
-(Tried to) Silence ./autogen.sh launching screen
-Edited some comments
Better SDL installation handling

-Function install_sdl is conditioned for cases with lack of connection
and/or lack of the SDL2 folder
-Function makeItHappen is given the proper argument in install_sdl
-Function install_sdl_libs is ready to skip support libraries that
aren’t downloaded
-Renamed $format to $fileExt
-Added proper procedure in “noSDL”
-Edited some comments
-Minor adjustments
Installation of requirements (+ fix)

-Function main now calls for requirements in case there’s an internet
connection
-cd $homeplace should happen after each support library installation,
not at the very end
Better install_sdl_libs handling

-Function install_sdl_libs proper handles support libs downloading and
their installation
-$availableSups=$supportLibs in case there’s an internet connection
-Relocated cd $homeplace