#980 pkgconfig file needs to be edited when built without exif support

[Pacho Ramos]

We need to run this sed for a long time when building without exif support:
sed -i "s/, @REQUIREMENTS_FOR_LIBEXIF@//" libgphoto2.pc.in

Thanks for solving this

[Marcus Meissner]

i think i fixed the m4 snippet responsible for leaving this in now.

[Marcus Meissner]

in 2.5.5