* The getLine and getColumn functions need to update the position, or
they will return stale data for buffered streams. This fixes a bug in
the clang -analyzer-checker-option-help option, which was not wrapping
the help text correctly when stdout is not a TTY.
* If the stream contains multi-byte UTF-8 sequences, then the whole
sequence needs to be considered to be a single character. This has the
edge case that the buffer might fill up and be flushed part way
through a character.
* If the stream contains East Asian wide characters, these will be
rendered twice as wide as other characters, so we need to increase the
column count to match.
This doesn't attempt to handle everything unicode can do (combining
characters, right-to-left markers, ...), but hopefully covers most
things likely to be common in messages and source code we might want to
print.
Differential revision: https://reviews.llvm.org/D76291
e80b81d1cb