Merge branch 'v2.3' into v2.4

.travis.yml

@@ -131,7 +131,7 @@ install:
 # then replace doxygen with the desided version
 # I use 1.8.10 instead of 1.8.11 since it looks like 1.8.11 have troubles with
 # non case sensitive files (it writes capitalized filenames)
-  - if test "$MAKEDOC" == yes ; then ./.travis/install.doxygen Release_1_8_13 ; fi
+  - if test "$MAKEDOC" == yes ; then ./.travis/install.doxygen Release_1_8_14 ; fi
   - if test "$VALGRIND" == yes ; then sudo apt-get install -y valgrind           ; fi
   - if test "$LAPACK" == yes ; then sudo apt-get -y install libatlas-base-dev      ; fi
 # moreover, we hardcode path to dynamic library, required for xdrfile to link properly

CHANGES/v2.3.md

@@ -216,4 +216,9 @@ For developers:
 - Solved small bug in stored PLUMED_ROOT directory as obtained from statically patched MD codes.
   Namely, the compilation directory was stored rather than the installation one.
 
+## Version 2.3.5
+
+For developers:
+- Doxygen on travis-ci has been updated to 1.8.14
+