Fix DOXY file

src/docs/Doxyfile

@@ -1645,6 +1645,11 @@ ALLEXTERNALS           = NO
 
 EXTERNAL_GROUPS        = YES
 
+# The PERL_PATH should be the absolute path and name of the perl script
+# interpreter (i.e. the result of `which perl').
+
+PERL_PATH              = /usr/bin/perl
+
 #---------------------------------------------------------------------------
 # Configuration options related to the dot tool
 #---------------------------------------------------------------------------
@@ -1657,6 +1662,15 @@ EXTERNAL_GROUPS        = YES
 
 CLASS_DIAGRAMS         = NO
 
+# You can define message sequence charts within doxygen comments using the \msc
+# command. Doxygen will then run the mscgen tool (see
+# http://www.mcternan.me.uk/mscgen/) to produce the chart and insert it in the
+# documentation. The MSCGEN_PATH tag allows you to specify the directory where
+# the mscgen tool resides. If left empty the tool is assumed to be found in the
+# default search path.
+
+MSCGEN_PATH            =
+
 # If set to YES, the inheritance and collaboration graphs will hide
 # inheritance and usage relations if the target is undocumented
 # or is not a class.