xz, xzdec, lzmainfo: Use tuklib_attr_noreturn.

xz, xzdec, lzmainfo: Use tuklib_attr_noreturn.

For compatibility with C23's [[noreturn]], tuklib_attr_noreturn
must be at the beginning of declaration (before "extern" or
"static", and even before any GNU C's __attribute__).

This commit also moves all other function attributes to
the beginning of function declarations. "extern" is kept
at the beginning of a line so the attributes are listed on
separate lines before "extern" or "static".