Bug #1251

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

test/width.t.cpp

@@ -27,6 +27,7 @@
 
 #include <cmake.h>
 #include <iostream>
+#include <stdlib.h>
 #include <text.h>
 #include <test.h>
 
@@ -35,6 +36,10 @@ int main (int argc, char** argv)
 {
   UnitTest t (16);
 
+  // Ensure environment has no influence.
+  unsetenv ("TASKDATA");
+  unsetenv ("TASKRC");
+
   t.is (mk_wcwidth ('a'),    1, "U+0061 --> 1");
 
   t.is (mk_wcwidth (0x5149), 2, "U+5149 --> 2");