Accept other leptonica's names

[glu8716]

On ArchLinux the required library liblept.so is actually called libleptonica.so. I had to make the following symlink in order to make PgsToSrt to read it: ln -s /usr/lib/libleptonica.so.6 /usr/lib/liblept.so.5. Would be good if the program could read the name libleptonica.so by itself.

[Tentacule]

I added new command line parameters to override leptonica's name/version in this release

In your case adding this should work : --libleptname leptonica --libleptversion 6