Fix doxygen test

Fix doxygen test for python 3.6 since a modification in re module:

Changed in version 3.6: Unknown escapes consisting of '' and an ASCII letter now are errors.

Source : https://docs.python.org/3/library/re.html

Utilities/Doxygen/mcdoc.py

@@ -81,9 +81,9 @@ def checkGroup( fname, group ):
     # we don't care about doxygen fields not about a class
     if r"\class" in dcontent and dcontent != " \class classname ":
       # do we have a line with the expected content?
-      if not re.search(r"\ingroup .*"+group+"( |$)", dcontent, re.MULTILINE):
+      if not re.search(r"\\ingroup .*"+group+"( |$)", dcontent, re.MULTILINE):
         # get class name and the line for debug output
-        cname = re.search(r"\class +([^ ]*)", dcontent).group(1).strip()
+        cname = re.search(r"\\class +([^ ]*)", dcontent).group(1).strip()
         line = len(fcontent[:m.start(1)].splitlines())
         sys.stderr.write(r'%s:%s: error: "\ingroup %s" not set in class %s.' % (fname, line, group, cname) +"\n")
         ret = 1