Merge branch 'v2.1' into v2.2

CHANGES/v2.1.txt

@@ -244,6 +244,9 @@ For users:
 Unreleased changes (will be included in 2.1.5)
 ---------------------------------------------
 
+For users:
+- PLUMED now reports an error when using \ref HISTOGRAM with FREE-ENERGY without USE_ALL_DATA. See \issue{175}
+
 See branch \branch{v2.1} on git repository.
 
 

src/analysis/Histogram.cpp

@@ -236,6 +236,7 @@ void Histogram::performAnalysis(){
 
   Grid* gg; IFile oldf; oldf.link(*this); 
   if( usingMemory() && oldf.FileExist(gridfname) ){
+      if(fenergy) error("FREE-ENERGY only works with USE_ALL_DATA");
       oldf.open(gridfname);
       gg = Grid::create( "probs", getArguments(), oldf, gmin, gmax, gbin, false, false, false );
       oldf.close();