scanner.c edits
Merge branch 'master' of https://github.com/dougdliu/CSE-220-Lab-3
updated get_char to fill source_buffer
Merge branch 'master' of https://github.com/dougdliu/CSE-220-Lab-3
get_char updates
Merge branch 'master' of https://github.com/dougdliu/CSE-220-Lab-3