Stephen Webb's staging headers patch

[David Edelsohn]

>>>>> Gabriel Dos Reis writes:

Gabriel> If the patch works for you (i.e. AIX with multilib), then please check
Gabriel> it in on mainline and branch.  I'd encourage people having troubles
Gabriel> with src/gen-num-limits.cc on some "exotic" plateforms to test David's
Gabriel> patch.

	I have committed the patch to the mainline.

	This is only the first step.  configure still needs to set
GLIBCPP_IS_CROSS_COMPILING at some point.  I don't know whether AIX should
do this before all of the tests and define the macros like the GNU/Linux
cross-compiling case or somehow set the macro at the end after all of the
tests have ben performed.

	Something similar needs to be done for the other 64-bit platforms,
so *WE* (ALL OF US) need to design a general mechanism for this.

David