Warning in case of usage of a single quote in a code span.

When we have a single quotes in a codespan we can get the warning:
```
warning: found </c> tag without matching <c>
```
Added the workaround to the documentation.

1 files changed, 6 insertions, 1 deletions

diff --git a/doc/markdown.doc b/doc/markdown.doc
index 5edbaf9..883e831 100644
--- a/doc/markdown.doc
+++ b/doc/markdown.doc
@@ -193,10 +193,12 @@ code spans appear inline in a paragraph. An example:
 
     Use the `printf()` function.
 
-To show a literal backtick inside a code span use double backticks, i.e.
+To show a literal backtick or single quote inside a code span use double backticks, i.e.
 
     To assign the output of command `ls` to `var` use ``var=`ls```.
 
+    To assign the text 'text' to `var` use ``var='text'``.
+
 See section \ref mddox_code_spans for more info how doxygen handles
 code spans slightly different than standard Markdown.
 
@@ -606,6 +608,9 @@ In other words; a single quote cancels the special treatment of a code span
 wrapped in a pair of backtick characters. This extra restriction was
 added for backward compatibility reasons.
 
+In case you want to have single quotes inside a code span, don't use 
+one backtick but two backticks around the code span.
+
 \subsection mddox_lists Lists Extensions
 
 With Markdown two lists separated by an empty line are joined together into