New wxHashTable implementation when wxUSE_STL == 1. Replaces

  New wxHashTable implementation when wxUSE_STL == 1. Replaces
the old implementation based upon wxHashMap. Removed support
for wxHashTable in wxHashMap.
  Rationale: using wxHashMap for wxHashTable implementation required
special support in wxHashMap. This precluded using STL-provided
hash_map to implement wxHashMap. This new implementation does not
use keyed wxList interface and should be almost totally compatible
with the old non-STL wxHashTable.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@24638 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775