hghave.py: fix matchoutput documentation

dispatch: use versiontuple() We have a new generic function for this. Use it.

util: add versiontuple() for returning parsed version information We have similar code in dispatch.py. Another consumer is about to be created, so establish a generic function in an accessible location.

extensions: rename _ignore to _builtin, add descriptive comment It was previously not at all obvious what this was for. We also change it to a set to avoid iterating over an admittedly small list repeatedly at startup time.

ui: avoid needless casting to a str In many cases, we don't need to cast to a str because the object will be cast when it is eventually written. As part of testing this, I added some code to raise exceptions when a non-str was passed in and wasn't able to trigger it. i.e. we're already passing str into this function everywhere, so the casting isn't necessary.

ui: remove labeled argument from popbuffer It was moved to pushbuffer and currently does nothing.

color: evaluate labels at write time Previously, we stored 2-tuples of text and label in a list and then evaluated the labels when the buffer was popped. After this patch, we evaluate the labels at write time and do a simple join when the buffer is popped. This patch appears to have no impact on performance, despite creating fewer 2-tuples and having fewer strings hanging around in memory.