add a pkgconfig template about npapi-sdk HOT 6 OPEN

Right now, the pkg-config filenames are broken by design. I guess Mozilla 
thinks it's funny when random packages look for 6 different pkgconfig package 
names to find NPAPI headers, and I don't think adding 7th there is really a 
good solution. I'd go with using 'mozilla-plugin' which seems to be the most 
widespread one.

My implementation:
- https://github.com/mgorny/npapi-sdk/commit/66c583ee27

Though it will still need a few more commits to make any real-life plugin 
buildable with it.

Gentoo contributor - I'm really happy that you're interested in helping here 
(thanks for the patch), but please keep it professional. No need for the snarky 
comments. We're also just trying to help and perhaps not responsible for what 
you think we are anyway.

I'd be happy to take a patch for this, let me know when it is done and ask 
Wolfgang (the reporter of this bug) for review?

Ok, after some discussion I've recreated the patch to use a clean, new 
npapi-sdk.pc file for it. This patch relies on my other autotools patch but the 
file can be rebased easily if you're really against having a buildsystem. But 
please remember to replace @VERSION@ with the actual NPAPI version (0.27) as 
some upstreams really want to be able to check for the version.

If the patch gets a clean-go, I could start requesting plugin upstreams to use 
that pkg-config file instead/next-to the random stuff they do now.

What Wolfgang created is 
https://build.opensuse.org/package/view_file?project=mozilla%3AFactory&package=n
papi-sdk&file=npapi-sdk.pc.in. It's basically the same, and in any case I don't 
think Wolfgang or anybody else really cares about the details. The only think 
we need is you to provide ANY pkg-config file so plugin creators can start 
searching for it.

+1 to commit Gentoo's patch.

I don't want to argue about buildsystem or not but I'd like a de-facto standard 
with pkg-config file naming. The contents like the includedir can still be 
modified from downstream maintainers but the consuming packages should only 
have to care about one pkg-config file name. So review+ for the npapi-sdk.pc 
name and content. If it's preprocessed or not is another issue.