man: fix a few bogus entries in directives index

When wrong element types are used, directives are sometimes placed in the wrong
section. Also, strip part of text starting with "'", which is used in a few
places and which is displayed improperly in the index.

tools/make-directive-index.py

@@ -190,7 +190,7 @@ def _extract_directives(directive_groups, formatting, page):
                 stor[text].append((pagename, section))
                 if text not in formatting:
                     # use element as formatted display
-                    if name.text[-1] in '= ':
+                    if name.text[-1] in "= '":
                         name.clear()
                     else:
                         name.tail = ''