Generate links in man page

Some [foo](bar) links were added to manual.yml without updating
build_manpage.py to make it generate roff for "a" tags.

Fixes #2930

docs/build_manpage.py

@@ -81,11 +81,14 @@ def _walk(self, root, parent_tag=None):
                 text = ''.join(root.itertext()).strip()
                 self.__write_cmd('.SS "{}"'.format(self._h3_sanitize(text)))
 
-            elif root.tag == 'p':
+            elif root.tag in 'p':
                 if last_tag not in ['h2', 'h3'] and parent_tag not in ['li']:
                     self.__write_cmd('.P')
                 self._write_element(root, ensure_newline=(parent_tag != 'li'))
 
+            elif root.tag in 'a':
+                self._write_element(root, ensure_newline=(parent_tag != 'li'))
+
             elif root.tag == 'ul':
                 if self._ul_is_special(root):
                     li = root[0]