[ARM] Fix ld.so crash when built using Binutils 2.29

[Jiong Wang]

Hi,

   There is bug report that ld.so in GLIBC 2.24 built by Binutils 2.29 will crash
on arm-linux-gnueabihf.  This is confirmed, and the details is at:

    https://sourceware.org/bugzilla/show_bug.cgi?id=21725.

   And I could also reproduce this crash using GLIBC master.

   As analyzed in the PR, the old code was with the assumption that assembler
won't set bit0 of thumb function address if it comes from PC-relative
instructions and the calculation can be finished during assembling.  This
assumption however does not hold after PR gas/21458.

   I think ARM backend in GLIBC should be fix to be more portable so it could
work with various combinations of GLIBC and Binutils.

   OK for master and backport to all release branches?


2017-07-12  Jiong Wang  <jiong.wang@arm.com>

         * sysdeps/arm/dl-machine.h (elf_machine_load_address):  Also strip bit 0
         of pcrel_address under Thumb mode.

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