Fix relative paths for VimwikiRenameLink. Merge PR #787.

Fixes #90 

__Problem__: VimwikiRenameLink does not rename dir1/toto url in dir2/tata
because the dirs (dir2 and .) were well crossed but badly inspected.
__Solution__: `blob(.ext*)` -> `glob(**/*.ext)` + find the relative URL

* Fasten: VimwikiRenameLink goes faster with cache
More: To compute old_url regex, use a cache dict because it is the same
for files in the same directories

* Util DeleteHiddenBuffer -> do not delete Vader buffer

* Test: Prettify: Util: teardown delete defined function

* Remove unnecessary trailing spaces
Note: list_VimwikiReturn.vader has some necessary trailing spaces

doc/vimwiki.txt

@@ -3471,6 +3471,7 @@ Contributors and their Github usernames in roughly chronological order:
     - Robin Lowe (@defau1t)
     - Abhinav Gupta (@abhinav)
     - Dave Gauer (@ratfactor)
+    - Martin Tourneboeuf (@tinmarino)
 
 
 ==============================================================================
@@ -3486,6 +3487,8 @@ https://github.com/vimwiki-backup/vimwiki/issues.
 2.5 (in progress)~
 
 New:~
+    * PR #787: |:VimwikiRenameLink| works for all directories: even
+      wiki_root/diary/2019-12-11.md if current file is wiki_root/dir1/file.md.
     * Add support for markdown indented code blocks.
     * Issue #764: fenced code blocks are properly supported for markdown
       syntax i.e. more than 3 backticks, adds tilde support.
@@ -3561,6 +3564,7 @@ Removed:~
       point.
 
 Fixed:~
+    * Issue #90: VimwikiRenameLink doesn't update links in diary.
     * Issue #796: Rename |:VimwikiGenerateTags| to |:VimwikiGenerateTagLinks|
     * Issue #790: Allow tags before a header with markdown syntax.
     * Issue #779: Vimwiki tags file meets ctags standard.