Run clang-modernize on things

aegisub/libaegisub/common/charset.cpp

aegisub/libaegisub/common/charset_conv.cpp

aegisub/libaegisub/common/dispatch.cpp

aegisub/libaegisub/common/mru.cpp

aegisub/libaegisub/common/option_visit.cpp

aegisub/libaegisub/common/path.cpp

aegisub/libaegisub/common/vfr.cpp

aegisub/libaegisub/include/libaegisub/cajun/reader.h

aegisub/libaegisub/include/libaegisub/cajun/writer.h

aegisub/libaegisub/include/libaegisub/exception.h

aegisub/libaegisub/include/libaegisub/hotkey.h

aegisub/libaegisub/include/libaegisub/line_iterator.h

aegisub/libaegisub/include/libaegisub/line_wrap.h

aegisub/libaegisub/include/libaegisub/log.h

aegisub/libaegisub/include/libaegisub/mru.h

aegisub/libaegisub/include/libaegisub/signal.h

aegisub/libaegisub/include/libaegisub/vfr.h

aegisub/src/aegisublocale.cpp

aegisub/src/ass_attachment.cpp

aegisub/src/ass_dialogue.cpp