ValuePairs: fixed some memory leak

  * free all the content of the g_ptr_array, not just the array itself
    (Viktor Tusa fixed it in 3.6)
  * free the g_ptr_array() when failed to split the vp names
    (found by Balazs Scheidler)
Merge pull request #126 from lmesz/3.5/master

ValuePairs: free the content of the value-pairs array not just the array...