Remove constant offsets from video timestamps.

We had previously been assuming the audio started at 0, while
respecting the video PTS. If the PTS of the first video frame was
non-zero, this would lead to the video being delayed behind the audio
and never catching up.

Fixes #386.
Distribute the project given to android_build.

This fixes a bug where we would distribute the current project
instead of the one supplied on the command line, causing things
not to work.
Ignore profile_screen.txt when distributing.
Ignore tmp/ directory when navigating .rpy files.
Add a large-fonts mode to the launcher.

Fixes #399.
Ignore .rpyc files that cannot be loaded.

This makes it possible to version down if the .rpy file exists and
do not use any newer features.
Bump version to 6.17.7.
Include Ren'Py with android distributions.

RAPT will now use this version of Ren'Py, which can include patches
by the creator.

Fixes #368.