Add support for 'z' size format specifier.

Assume that non-MSVC compilers support it directly and use 'I' for MSVC.

Closes #16596.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78010 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/strings/vararg.cpp

@@ -36,6 +36,7 @@ private:
     CPPUNIT_TEST_SUITE( VarArgTestCase );
         CPPUNIT_TEST( StringPrintf );
         CPPUNIT_TEST( CharPrintf );
+        CPPUNIT_TEST( SizetPrintf );
 #if wxUSE_STD_STRING
         CPPUNIT_TEST( StdString );
 #endif
@@ -49,6 +50,7 @@ private:
 
     void StringPrintf();
     void CharPrintf();
+    void SizetPrintf();
 #if wxUSE_STD_STRING
     void StdString();
 #endif
@@ -138,6 +140,24 @@ void VarArgTestCase::CharPrintf()
     CPPUNIT_ASSERT_EQUAL( "value is 240 (int)", s );
 }
 
+void VarArgTestCase::SizetPrintf()
+{
+    size_t  i =  1;
+    ssize_t j = -2;
+
+    CPPUNIT_ASSERT_EQUAL
+        (
+            "size_t=1 ssize_t=-2",
+            wxString::Format("size_t=%zu ssize_t=%zd", i, j)
+        );
+
+    CPPUNIT_ASSERT_EQUAL
+        (
+            "size_t=0xA0",
+            wxString::Format("size_t=0x%zX", static_cast<size_t>(160))
+        );
+}
+
 #if wxUSE_STD_STRING
 void VarArgTestCase::StdString()
 {