arm.c (arm_cpp_interwork): New variable.

* arm.c (arm_cpp_interwork): New variable.
(arm_override_options): Set it if TARGET_INTERWORK was on the command
line.
* arm.h (arm_cpp_interwork): Declare it.
(TARGET_CPU_CPP_BUILTINS): Use it to control definition of
__THUMB_INTERWORK__ in the preprocessor.

From-SVN: r84351