Merge remote-tracking branch 'origin/master' into feature/to_string
# Conflicts:
# include/etl/basic_format_spec.h
# include/etl/private/to_string_helper.h
# include/etl/to_string.h
# include/etl/to_u16string.h
# include/etl/to_u32string.h
# include/etl/to_wstring.h
# test/test_to_string.cpp
# test/test_to_u16string.cpp
# test/test_to_u32string.cpp
# test/test_to_wstring.cpp
