Bug #1251

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

test/config.t.cpp

@@ -27,6 +27,7 @@
 
 #include <cmake.h>
 #include <iostream>
+#include <stdlib.h>
 #include <Context.h>
 #include <test.h>
 
@@ -37,6 +38,10 @@ int main (int argc, char** argv)
 {
   UnitTest t (11);
 
+  // Ensure environment has no influence.
+  unsetenv ("TASKDATA");
+  unsetenv ("TASKRC");
+
   Config c;
 
   // void set (const std::string&, const std::string&);