[PATCH, resend] ARM: fix inline atomic handling ldrex/strex

[Tim Northover]

Hi,

I still think that this is pretty much the right solution: any
environment compiling for an architecture that has ldrex/strex but
doesn't want to use it should add some specific override. They seem to
be in a massive minority. If they don't want to add their own OS to
the triple they can try for a -mwhatever option (patches welcome, or
at least grudgingly accepted).

That said, this patch doesn't have any tests. We really need those to
make sure no-one inadvertently changes this behaviour in future (if
nothing else).

Cheers.

Tim.