Bug #1251

- #1251 tests should sanitize TASKDATA and TASKRC env vars (thanks to Jakub
  Wilk).

test/nibbler.t.cpp

@@ -26,6 +26,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include <cmake.h>
+#include <stdlib.h>
 #include <Context.h>
 #include <Nibbler.h>
 #ifdef NIBBLER_FEATURE_DATE
@@ -52,6 +53,10 @@ int main (int argc, char** argv)
 #endif
 #endif
 
+  // Ensure environment has no influence.
+  unsetenv ("TASKDATA");
+  unsetenv ("TASKRC");
+
   try
   {
     Nibbler n;