docs: fix HTML word wapping in table cells

The sphinx_rtd_theme does not properly handle wrapping long lines in
table cells when rendering to HTML due to a CSS issue (see
readthedocs/sphinx_rtd_theme#1505).

Until the issue is fixed upstream in sphinx_rtd_theme, we can simply
override the CSS here.  This commit overrides the CSS in conf.py and
also touches up some places where we previously tried to work around
the lack of word wrapping.

Signed-off-by: Jeff Squyres <jeff@squyres.com>

docs/conf.py

@@ -195,3 +195,16 @@
 .. |flex_min_version| replace:: {flex_min_version}
 
 """
+
+# The sphinx_rtd_theme does not properly handle wrapping long lines in
+# table cells when rendering to HTML due to a CSS issue (see
+# https://github.com/readthedocs/sphinx_rtd_theme/issues/1505).  Until
+# the issue is fixed upstream in sphinx_rtd_theme, we can simply
+# override the CSS here.
+rst_prolog += """
+.. raw:: html
+
+   <style>
+   .wy-table-responsive table td,.wy-table-responsive table th{white-space:normal}
+   </style>
+"""