Further fixes for GDB server on Thumb code:

Further fixes for GDB server on Thumb code:

* Disabled several tests on ARM when gdb version < 7.1
  gdb 7.0 has problems with next/step/... in ARM thumb code.

* Documented in manual-core.xml that ARM thumb code implies
  a gdb version >= 7.1

* m_gdbserver.h/.c : take into account the thumb bit at several places

* use new IRStmt_IMark::delta field to distinguish ARM vs Thumb
  instructions as committed in vex r2153

Patch from bug 214909 comment 99 (valgrind part).
(Philippe Waroquiers, philippe.waroquiers@skynet.be)

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11779