As suggest here:
https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute-Syntax
"You may optionally specify attribute names with ‘__’ preceding and
following the name. This allows you to use them in header files without
being concerned about a possible macro of the same name. For example,
you may use the attribute name __noreturn__ instead of noreturn. "
It also used __bitwise and __force. It seems easier to rename
our versions since they are local to this one single header.
Also, undefine them afteerwards, so that we don't pollute the
preprocessor macro namespace.
