Don't always turn on wxTE_PROCESS_ENTER in wxOSX

This style was unconditionally used for all multiline controls for some
reason, meaning that wxEVT_TEXT_ENTER could be received even for the controls
not using wxTE_PROCESS_ENTER explicitly, which was unexpected.

Don't do this any more to conform to the expected behaviour.

Also do use wxTE_PROCESS_ENTER for the text control supposed to allow handling
"Enter" in the text sample: surprisingly, it didn't have this style before,
although it was clearly supposed to.

Closes #1913.

src/osx/textctrl_osx.cpp

@@ -103,14 +103,6 @@ bool wxTextCtrl::Create( wxWindow *parent,
     if ( !wxTextCtrlBase::Create( parent, id, pos, size, style & ~(wxHSCROLL | wxVSCROLL), validator, name ) )
         return false;
 
-    if ( m_windowStyle & wxTE_MULTILINE )
-    {
-        // always turn on this style for multi-line controls
-        m_windowStyle |= wxTE_PROCESS_ENTER;
-        style |= wxTE_PROCESS_ENTER ;
-    }
-
-
     SetPeer(wxWidgetImpl::CreateTextControl( this, GetParent(), GetId(), str, pos, size, style, GetExtraStyle() ));
 
     MacPostControlCreate(pos, size) ;