A better fix for wxHash{Map,Set} with g++ 4.7.

This reverts r70556, i.e. removes the scope operators added by it to all
WX_DECLARE_HASH_{MAP,SET} macros, and implements a workaround for the problem
due to the use of empty base class optimization in g++ 4.7 standard library
implementations inside the macros themselves by prepending the hasher and
comparator classes with explicit "struct".

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72297 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/hashmap.h

@@ -83,8 +83,8 @@
     @code
     WX_DECLARE_HASH_MAP( int,
                          wxString,
-                         ::wxIntegerHash,
-                         ::wxIntegerEqual,
+                         wxIntegerHash,
+                         wxIntegerEqual,
                          MyHash );
 
     // using an user-defined class for keys
@@ -119,8 +119,8 @@
 
     WX_DECLARE_HASH_MAP( MyKey,      // type of the keys
                          SOME_TYPE,  // any type you like
-                         ::MyKeyHash,  // hasher
-                         ::MyKeyEqual, // key equality predicate
+                         MyKeyHash,  // hasher
+                         MyKeyEqual, // key equality predicate
                          CLASSNAME); // name of the class
     @endcode