Add docs for the ic text object

This addresses tomtom#255 and
tomtom#188. It also partially
addresses tomtom#237 (by making
it clear that the functionality exists, even if it doesn't quite do
what's being asked for there).

doc/tags

@@ -56,4 +56,5 @@ tcomment-debug	tcomment.txt	/*tcomment-debug*
 tcomment-maps	tcomment.txt	/*tcomment-maps*
 tcomment-new-filetype	tcomment.txt	/*tcomment-new-filetype*
 tcomment-operator	tcomment.txt	/*tcomment-operator*
+tcomment-textobject	tcomment.txt	/*tcomment-textobject*
 tcomment.txt	tcomment.txt	/*tcomment.txt*

doc/tcomment.txt

@@ -121,6 +121,14 @@ A secondary set of key maps is defined for normal and insert mode (see also
     <Leader>__       :: :TComment
     <Leader>_i       :: :TCommentInline
 
+                                              *tcomment-textobject*
+
+A text object is also added for selecting an inner-comment:
+
+    {operator}ic :: Operate on the inner comment. The mapping can be changed
+                    using the `g:tcomment_textobject_inlinecomment` variable
+                    or disabled by setting it to the empty string, `''`.
+
 
 
 -----------------------------------------------------------------------
@@ -256,6 +264,10 @@ g:tcomment_mapleader_uncomment_anyway (default: 'g<')
 g:tcomment_mapleader_comment_anyway (default: 'g>')
     See |tcomment-operator|.
 
+                                                    *g:tcomment_textobject_inlinecomment*
+g:tcomment_textobject_inlinecomment (default: 'ic')
+    See |tcomment-textobject|.
+
                                                     *:TComment*
 :[range]TComment[!] ?ARGS...
     If there is a visual selection that begins and ends in the same line,