overlay: fix video-top property
feature: remove double free
display: lack of format-string causing a compiler warning
filter: improve error handling
filtershader: fix string format compiler warnings
bumper: error out properly if we cannot load the png file
display: properly shutdown if we error after context creation

The _finalize() code checks to see if the context was created before
attempting to destroy it.  We never did say that we had created the context.
bumper: nicer error for no bumpmap file proveded