PCH is used only for the first header

[Briltz, Denis]

>> 
>> My point was that gcc uses pch only for the _first_ included header and
this
>> is not documented.

>This is a simplification of the actual rules.  The documentation
>completely describes what actually happens.  For instance, if 'a.h' is
>completely empty, and there is no PCH for it, a PCH for 'b.h' can be used.

>-- 
>- Geoffrey Keating <geoffk@geoffk.org>

Right, "a.h" contains macros affecting "b.h" and this is the reason why
"b.h.gch" was not used.
Thanks,
Denis.