swscanf and vswscanf implementation proposal

src/header/wchar/lookaheadreader.rs

src/header/wchar/mod.rs

src/header/wchar/wscanf.rs

tests/Makefile

tests/expected/bins_static/wchar/wscanf.stderr

tests/expected/bins_static/wchar/wscanf.stdout

tests/wchar/wscanf.c