Properly handle script blocks in strict mode.

(That is, markdown-markdown_in_html_blocks.)
Previously a spurious `<p>` tag was being added.

Closes #1093.
Docbook reader: Avoid failure if tbody contains no tr or row elements.
LaTeX reader: Support babel-style quoting: `` "`..."' ``.
LaTeX writer: Factored out function for table cell creation.
LaTeX writer:  Better treatment of footnotes in tables.

Notes now appear in the regular sequence, rather than in the
table cell.  (This was a regression in 1.10.)