Allows Windows users to put SDL2 folder in %HIFI_LIB_DIR% folder (see BUILD.md for info about %HIFI_LIB_DIR% environment variable)
removed duplicate hints entries
Moved the new hints to HINTS, thanks for the hint @birarda
Merge pull request #3624 from thoys/sdl2-find-hifi_libs

Allow "%HIFI_LIB_DIR%/SDL2" for SDL2 path on Windows