* Documentation/user/tutorial.itely (Running LilyPond): Mention

* Documentation/user/tutorial.itely (Running LilyPond): Mention
xdvi and XFree86 option for Windows users.

* Documentation/user/invoking.itexi: Add ly2dvi's -p alias.

* scripts/ly2dvi.py: Bugfix for `ly2dvi -I ./foo foo.ly'.  Also
append directory of first file to search path, allowing
`ly2dvi	foo/foo.ly' when foo.ly includes other files from
directory foo.  Add short option alias '-p' for --pdf.