The uc_mcontext.__reserved member of ucontext_t is a user visible API,
that should not be changed, because this is the only way to access cpu
states of various extensions of linux asm/sigcontext.h, it does not
violate namespace rules either, so revert this part of the commit
commit 4fa9b3bfe6759c82beb4b043a54a3598ca467289
Commit: Joseph Myers<joseph@codesourcery.com>
Fix mcontext_t sigcontext namespace (bug 21457).
(In principle the user can type cast &uc_mcontext to struct sigcontext*
to use the linux sigcontext fields, but that's not the existing practice
since mcontext_t used to be a typedef of struct sigcontext.)
I plan to commit this soon for 2.27 and backport it to 2.26 if there are
no comments.