[oe] pkgconfig bbclass: also sed out bogus includes

[Sebastian Spaeth]

> author	Koen Kooi <koen at openembedded.org>
> commit	2c8134baa56ad047f5c37069379c0e560dd6477e
>
> RP says: In theory the recipes themselves should be patched to stop
> this nonesense getting in there in the first place but that is
> appropriate for pkgconfig.bbclass

Nice one. Should we add a warning when we find such a bogus include so
recipes can be fixed up over time?

Sebastian