Track nested loop levels in CMake language with a stack of counters

It gets incremented while entering a loop block (e.g. foreach or while)
and gets decremented when leaving the block. Because scope borders for
example at function borders must be taken into account the counter is
put into a stack. With every new scope an empty counter is pushed on the
stack, when leaving the scope the original value is restored.

This will allow easy querying if the break command is properly nested
within a loop scope.

Signed-off-by: Gregor Jasny <gjasny@googlemail.com>

Source/cmForEachCommand.cxx

@@ -27,6 +27,8 @@ IsFunctionBlocked(const cmListFileFunction& lff, cmMakefile &mf,
     // if this is the endofreach for this statement
     if (!this->Depth)
       {
+      cmMakefile::LoopBlockPop loopBlockPop(&mf);
+
       // Remove the function blocker for this scope or bail.
       cmsys::auto_ptr<cmFunctionBlocker>
         fb(mf.RemoveFunctionBlocker(this, lff));
@@ -73,6 +75,7 @@ IsFunctionBlocked(const cmListFileFunction& lff, cmMakefile &mf,
             }
           }
         }
+
       // restore the variable to its prior value
       mf.AddDefinition(this->Args[0],oldDef.c_str());
       return true;
@@ -199,6 +202,8 @@ bool cmForEachCommand
     }
   this->Makefile->AddFunctionBlocker(f);
 
+  this->Makefile->PushLoopBlock();
+
   return true;
 }
 
@@ -242,5 +247,8 @@ bool cmForEachCommand::HandleInMode(std::vector<std::string> const& args)
     }
 
   this->Makefile->AddFunctionBlocker(f.release()); // TODO: pass auto_ptr
+
+  this->Makefile->PushLoopBlock();
+
   return true;
 }