Adding target specific routines

[Paul Brook]

I'm currently adding ARM EABI support to libstdc++, and described in 
http://www.armdevzone.com/EABI/cppabi.pdf

Part of this requires adding several extra 'helper' functions to libsupc++ 
(Section 3.2.2.3 or the above document).

I'm currently adding a new file (arm_eabi.cc), and surrounding the file 
contents with #if defined(__arm__) && defined(__ARM_EABI__)

Is this the best way of doing things, or is there some other mechanism I 
should use/invent to conditionally add these routines?

Paul