Feature Request: Ignore anonymous option (#727)

Closes #726

New option `g:tagbar_ignore_anonymous` to ignore any tags with __anon in
the tag name. CTAGS will print any unlabeled tags with the __anon###
name with a custom hash. This option will ignore those tags and they
will not be visible in the tagbar window. This could potentially result
in unknown behavior when a parent object has been ignored in this way.
However these tags should then fall under the default hierarchy for that
particular kind.

autoload/tagbar.vim

@@ -1281,6 +1281,11 @@ function! s:ProcessFile(fname, ftype) abort
         if line =~# '^!_TAG_' || has_key(seen, line)
             continue
         endif
+        if g:tagbar_ignore_anonymous && line =~# '__anon'
+            call tagbar#debug#log('anonymous tag found - ignoring per tagbar configuration')
+            continue
+        endif
+
         let seen[line] = 1
 
         let parts = split(line, ';"')

doc/tagbar.txt

@@ -1140,6 +1140,17 @@ highlight the 'SOME_MACRO' tag.
 Example: >
         let g:tagbar_highlight_method = 'nearest'
 <
+                                                    *g:tagbar_ignore_anonymous*
+g:tagbar_ignore_anonymous~
+Default: 0
+
+If set, any '__anon' tags generated by ctags will be ignored and will not be
+displayed in the tagbar window. Note: this will also mean any child tags of
+that anonymous tag will also not be visible.
+
+Example: >
+    let g:tagbar_ignore_anonymous = 1
+<
 
 ------------------------------------------------------------------------------
 HIGHLIGHT COLOURS                                           *tagbar-highlight*

plugin/tagbar.vim

@@ -101,6 +101,7 @@ function! s:setup_options() abort
         \ ['left', 0],
         \ ['help_visibility', 0],
         \ ['highlight_method', 'nearest-stl'],
+        \ ['ignore_anonymous', 0],
         \ ['position', default_pos],
         \ ['previewwin_pos', previewwin_pos],
         \ ['scopestrs', {}],