We still ensure the old and new ones start, respectfully, with `a/` and
`b/`. Use with `stripLen` to ensure tha the old `a/` and `/b` are gone
if a new prefix is added.
Since glibc 2.26, struct ucontext no longer exists but is wrapped in a
typedef ucontext_t.
This is basically a backport of the patch to gcc version 4.5 which was
introduced by @vcunat in f04b64c1e97fcacf6a6272de5a0562ced97db436.
Building against x86_64-linux and i686-linux now succeeds.
Signed-off-by: aszlig <aszlig@nix.build>
Cc: @abbradar
