Allow the creator to cancel out of create file and generate translation.

Fixes #100.
Skip whitespace before default parameters and arguments.

Fixes #101.
Update ffdecode.c to work with newer libav.

This gets rid of deprecation warnings when building ffdecode.c, and
adds a dependency on the avsample library.
Fix one more deprecation with newer libav.
Revert "Update ffdecode.c to work with newer libav."

This reverts commit 1ffd4f97fc4457d2f813f5d0763b346030f929b0.
Make use of avresample optional.

This lets us compile on platforms that do not support it, using
the old audio_resample code.
Use secure permissions in zip and tar files.

Previously, we used 666 and 777, and expected the user's umask to take
care of adjusting the permissions. Unfortunately, info-zip overrides
the umask, writing world-writable files to disk.

Thanks to Spiky Caterpillar for the bug and the fix.
Allow * in classification patterns to match directories as well as
files.

Fixes #106.
Force font autohinting.

This was the behavior of of Ren'Py until switching to Freetype 2.4. The
autohinter more resembles the older Ren'Pys, seems to produce better
forms on most fonts, and fixes spacing issues on broken fonts.
Fix translation problem.

Returned the wrong value when we used RENPY_UPDATE_STRINGS
to translate a string with a {#translation_comment} in it.
Error message fix.
Remove assert statements.

Thes won't run when optimization is enabled, which is the default
for Ren'Py. It's better to eliminate them entirely, so we have
the same configuration in testing and production.
Bump version to 6.15.5.
Additive blending in the GL renderer.

This commit adds in the backend support, for varying the additive
blending factor.

Additive blending will not be added to the (mostly obsolete) software
renderer. Instead, added a way to test if the current renderer
supports additive blending.
Add additive blending to Transform.
Deal (improperly) with additive blending in the software renderer.

When additive blending is 1.0, the software renderer will not
display an image. This is probably preferable to the image
displaying incorrectly, since they're likely to be effect
images.
Deal with r.over in the sprite manager.
Document additive blending.
Add the Flatten displayable to Ren'Py.
Check in problems.rst.