Add llpp.19

Blurb:

llpp a graphical PDF viewer which aims to superficially resemble
less(1)

Changes:

* Optional fontconfig support
* Reorganized/improved help screen (Michael Asnes)
* History mode
    Somewhat breaking change, full paths are now stored not just file
    names. This mode is entered by default when llpp is invoked without
    a path to the document to be viewed.
* Bugfixes
Um? This script is invoked by opam travis buildscript and installs the dependencies. In saucy, the commented line above would work too, but libmupdf-dev in whatever Travis runs is too old, so I have to build it from source.