Exceptions Handling on PPC64 with clang - gnu ld bug identified

[Roman Divacky]

Hi,

In a followup to https://lists.freebsd.org/pipermail/freebsd-toolchain/2017-May/002961.html 
I attempted to fix gnu ld in base to fix the wrongly set bit.

The following patch http://www.vlakno.cz/~rdivacky/ppc64.exceptions.fix.patch
switches a few computations to happen in 64bits instead of 32bit and fixes the
wrong personality/LDSA info in binaries.

As a result clang compiled/assembled c++ binaries with EH start to work for me.

Can someone verify this works for everyone? I can see the same cast in upstream
binutils but in a couple more places, so this is probably not the final answer
but is good enough for me.

Thanks, Roman