Merge branch 'add_fwide' into 'master'

src/header/stdio/default.rs

src/header/stdio/helpers.rs

src/header/stdio/mod.rs

src/header/wchar/mod.rs

src/platform/types.rs

tests/Makefile

tests/expected/stdio/freopen.stdout

tests/expected/wchar/fwide.stderr

tests/expected/wchar/fwide.stdout

tests/stdio/freopen.c

tests/wchar/fwide.c