Emit C attributes via cbindgen

cbindgen.globdefs.toml

include/features.h

src/header/assert/cbindgen.toml

src/header/ctype/cbindgen.toml

src/header/dirent/cbindgen.toml

src/header/netdb/cbindgen.toml

src/header/pthread/cbindgen.toml

src/header/signal/cbindgen.toml

src/header/stdio/cbindgen.toml

src/header/stdlib/cbindgen.toml

src/header/sys_time/cbindgen.toml

src/header/sys_types/cbindgen.toml

src/header/termios/cbindgen.toml

src/header/time/cbindgen.toml

src/header/unistd/cbindgen.toml

src/header/utime/cbindgen.toml

src/header/wchar/cbindgen.toml

tests/Makefile

tests/ctype.c

tests/expected/features.stderr