Fix assertion failure on unmatched function or macro

The fix in commit v3.2.3~3^2 (Fix assertion failure on unmatched foreach
in function, 2015-05-18) broke handling of unmatched non-loop blocks
because it assumed all function blockers removed during error unwinding
were for loops, essentially switching the set of mishandled cases.

The purpose of the loop block push/pop operations is to define a scope
matching the lifetime of the loop function blockers.  Since our function
blockers already have the proper lifetime, simply move the push/pop
operations to their constructor/destructor.

Extend the RunCMake.Syntax test with a case covering this.

Source/cmWhileCommand.h

@@ -19,8 +19,8 @@
 class cmWhileFunctionBlocker : public cmFunctionBlocker
 {
 public:
-  cmWhileFunctionBlocker() {this->Depth=0;}
-  virtual ~cmWhileFunctionBlocker() {}
+  cmWhileFunctionBlocker(cmMakefile* mf);
+  ~cmWhileFunctionBlocker();
   virtual bool IsFunctionBlocked(const cmListFileFunction& lff,
                                  cmMakefile &mf,
                                  cmExecutionStatus &);
@@ -29,6 +29,7 @@ public:
   std::vector<cmListFileArgument> Args;
   std::vector<cmListFileFunction> Functions;
 private:
+  cmMakefile* Makefile;
   int Depth;
 };