As conf.py has now numfig = True, needed to modify accordingly test for
links in html output.
This topic branch fixes#2405, #2414, and also makes for latex(pdf)
functional hyperlinks to named references, but only for literal blocks
(code-block or literalinclude).
modified: tests/roots/test-directive-code/caption.rst
modified: tests/roots/test-directive-code/conf.py
new file: tests/roots/test-directive-code/namedblocks.rst
modified: tests/test_directive_code.py