Rule of dashes in RestructuredText tables not recognized by pandoc

[rbonvall]

RestructuredText tables may have horizontal rules made of dashes instead of equal signs.

Pandoc doesn't recognize these rules, and creates rows full of dashes instead.

This minimal example exposes the bug:

Example 1:

+------------------------+------------+----------+
| Header row, column 1   | Header 2   | Header 3 |
+========================+============+==========+
| body row 1, column 1   | column 2   | column 3 |
+------------------------+------------+----------+
| body row 2             | Cells may span        |
+------------------------+-----------------------+

Example 2:

====================  ==========  ==========
Header row, column 1  Header 2    Header 3
====================  ==========  ==========
body row 1, column 1  column 2    column 3
body row 2            Cells may span columns
====================  ======================

Example 3:

====================  ==========  ==========
Header row, column 1  Header 2    Header 3
--------------------  ----------  ----------
body row 1, column 1  column 2    column 3
body row 2            Cells may span columns
====================  ======================

Compare the PDFs generated by rst2latex and by pandoc.

My pandoc version:

$ pandoc -v
pandoc 1.9.4.2
Compiled with citeproc-hs 0.3.4, texmath 0.6.0.6, highlighting-kate 0.5.1.