Add @ingroup tags and another doxygen comment.

aegisub/reporter/aegisub.cpp

aegisub/reporter/aegisub.h

aegisub/reporter/include/platform.h

aegisub/reporter/main.cpp

aegisub/reporter/main.h

aegisub/reporter/name_map.cpp

aegisub/reporter/platform.cpp

aegisub/reporter/platform_unix.cpp

aegisub/reporter/platform_unix.h

aegisub/reporter/platform_unix_bsd.cpp

aegisub/reporter/platform_unix_bsd.h

aegisub/reporter/progress.cpp

aegisub/reporter/progress.h

aegisub/reporter/r_pre.h

aegisub/reporter/report.cpp

aegisub/reporter/report.h

aegisub/reporter/sha256.c

aegisub/reporter/sha256.h

aegisub/reporter/upload.cpp

aegisub/reporter/upload.h