[ARM] Implementation of R_ARM_TARGET1 relocation

This patch provides implementation of R_ARM_TARGET1 relocation with
configuration of its behaviour from a command line. This patch provides
two command line options for GnuLd driver: --arm-target1-rel and
--arm-target1-abs (similar to ld option names with extra prefix 'arm-').
So user may choose which behaviour of R_ARM_TARGET1 is preferred for his
implementation of libc.

Differential Revision: http://reviews.llvm.org/D8707

llvm-svn: 234009