This change adds infrastructure to represent inline markup in the AST,
implements parsing of some of the inline markup (*emphasis*, **strong
emphasis**, `interpreted text`, ``inline literal``), and XML generation
for these constructs for SourceKit clients to consume.
The parsing itself is incomplete for constructs not mentioned above.
Most notably, we don't parse hyperlinks, and we don't parse the
double-colon that changes the next paragraph into a literal block.
Swift SVN r22752
It does not yet understand a lot of ReST constructs, in particular, it does not
understand inline markup at all, but it is good enough to extract brief
comments.
The parser in BriefParser.cpp does not construct any ASTs or emit any warnings.
This is a special parser for brief comments that should be as fast as possible.
Real ReST parser will come later.
Swift SVN r15046
