TLS descriptors for ARM

[Nick Clifton]

Hi Nathan,

> This patch adds support for TLS descriptors for ARM. Refer to
> http://www.codesourcery.com/publications/RFC-TLSDESC-ARM.txt for the
> current specification.

> built and tested for arm-none-linux-gnueabi, ok?

Almost.  Please build and test an arm-netbsdelf toolchain.  I get some 
new failures with this:

   LD REGRESSION: TLS gnu shared library
   LD REGRESSION: TLS gnu shared library non-lazy
   LD REGRESSION: TLS long plt library
   LD REGRESSION: TLS long plt
   LD REGRESSION: TLS thumb1
   LD REGRESSION: TLS descseq relaxation v7
   LD REGRESSION: TLS descseq relaxation BE8

Which I believe is due to interworking discrepancies.

Cheers
   Nick