UTF8: Correct MSW issue with previous commit

Linux does not handle the resize command with wide-character extended
table UTF-8.  The solution did not work for W7-32bit.  This is a
compromise, attempting first the preferred, previous solution and
falling back to the secondary solution.

(cherry picked from commit 6106210c87)

common/utf8.cpp

@@ -201,9 +201,20 @@ bool IsUTF8( const char* aString )
 
 UTF8::UTF8( const wchar_t* txt )
 {
-    wxCharBuffer charbuf = wxSafeConvertWX2MB( txt );
+    try
+    {
+        size_t len = wcslen( txt ) * 4 + 1;
+        char temp[len];
+        wxConvUTF8.WC2MB( temp, txt, len );
+        m_s.assign( temp );
+    }
+    catch(...)
+    {
+        auto string = wxSafeConvertWX2MB( txt );
+        m_s.assign( string );
+    }
 
-    m_s.assign( charbuf.data() );
+    m_s.shrink_to_fit();
 }
 
 

tools/utf8_tests.cpp

@@ -15,13 +15,13 @@ void callee( const wxString& aString )
 
 int main( int argc, char** argv )
 {
-    UTF8        bozo = "ü";
+    UTF8        bozo = "This is a test of UTF-8: ü‱☺😕😱";
 
     callee( bozo );
 
     wxString s = bozo;
 
-    wxString b = bozo;
+    UTF8 b = s;
 
     if( s.IsEmpty() )
     {
@@ -30,8 +30,23 @@ int main( int argc, char** argv )
 
     if(  s != bozo.wx_str() )
     {
-        printf( "string miscompare\n" );
+        printf( "wxString conversion error\n" );
     }
 
+    if( b != bozo )
+    {
+        printf( "From string conversion error\n" );
+    }
+
+    auto pos = bozo.begin();
+    auto end = bozo.end();
+
+    while( pos != end )
+    {
+        printf( "%c", *pos++ );
+    }
+
+    printf("\n");
+
     return 0;
 }