[poppler] POPPLER_DATADIR

[Adam Batkin]

>> You know what would also be nice...(would you be open to a patch?) not
>> hardcoding POPPLER_DATADIR, since especially on Windows you never know
>> where it will be installed.
> 
> Patch pushed to the repo.
> 
> And we are always open to interesting patches, but what are you going to do to 
> search for the POPPLER_DATADIR? Check each and every directory?

Well, that's an interesting question.

First of all, the current #define set from the configure script makes a 
lot of sense to keep. It works great on Linux (and other UNIX-like 
systems) since there are standard well-known locations for things there.

I would perhaps allow that to be overridden in one (or both) of two ways:
- an environment variable (could just call it POPPLER_DATADIR)
- a global/static "Initialize Poppler" function that can be called by an 
application to set that (and who knows, maybe other things will come 
along). I imagine that this option wouldn't be too popular, however in 
cases where poppler is installed as an embedded library as part of a 
larger program, it would be very useful. The parent application would 
presumably know where it is installed, as well as its own private 
Poppler data, so it would be quite easy for the application to make a 
call to initialize Poppler.

I am of course open to other ideas too...

-Adam Batkin