[PATCH]: Fix PR middle-end/6123, cleanup defining __pic__/__PIC__

[Joseph S. Myers]

On Fri, 2 Apr 2004, Kaveh R. Ghazi wrote:

> The problem in PR 6123 is that the macro definitions of __pic__ and
> __PIC__ are set in a convoluted mess, and some platforms don't define
> them at all.  As noted in the PR, it was suggested by rth that we move
> these definitions out of individual config files into the generic
> infrastructure.  Here's my attempt to do so.

These macros should also have documentation in cpp.texi.

-- 
Joseph S. Myers
jsm@polyomino.org.uk