libcapsppd: dealing with PPD files

The libcapsppd deals with PPD files (aka. Postscript Printer Description).

PPD files are created on the fly from a generic printer description (refer caps_ppd_base).

The other way round it can also read in a PPD file and provides its content in a key/value store manner.

This library requires libcapsbase, libcapstable, libcapsinif and libpaper.