stdio: Clean up __libc_message after unconditional abort

Since commit ec2c1fce ("malloc:
Abort on heap corruption, without a backtrace [BZ #21754]"),
__libc_message always terminates the process.  Since commit
a289ea09 ("Do not print backtraces
on fatal glibc errors"), the backtrace facility has been removed.
Therefore, remove enum __libc_message_action and the action
argument of __libc_message, and mark __libc_message as _No_return.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>