Syntax highlighting: reStructuredText (rst)

rst mode depends on stex mode and makes use of overlay.

[1] works nicely on CM3 4.9 version [2], so [3] is fixed now.

Bug: issue 2779
[1] https://ceres-solver-review.googlesource.com/#/c/5683/18/docs/source/faqs.rst
[2] http://imgur.com/y8QEylt
[3] https://github.com/codemirror/CodeMirror/issues/2850
Change-Id: I03f134aadbb8c2c3c2a8d3dc027d2b7f234cd176
5 files changed