Added some hints for translators in wxPG.

Because context of some texts to be translated can be unclear added some instructions for translators which can be extracted by gettext or similar tools.

src/propgrid/propgrid.cpp

@@ -204,7 +204,9 @@ wxPGGlobalVarsClass::wxPGGlobalVarsClass()
 {
     wxPGProperty::sm_wxPG_LABEL = new wxString(wxPG_LABEL_STRING);
 
+    /* TRANSLATORS: Name of Boolean false value */
     m_boolChoices.Add(_("False"));
+    /* TRANSLATORS: Name of Boolean true value */
     m_boolChoices.Add(_("True"));
 
     m_fontFamilyChoices = NULL;
@@ -404,6 +406,7 @@ void wxPropertyGrid::Init1()
 
     m_width = m_height = 0;
 
+    /* TRANSLATORS: Text  displayed for unspecified value */
     m_commonValues.push_back(new wxPGCommonValue(_("Unspecified"), wxPGGlobalVars->m_defaultRenderer) );
     m_cvUnspecified = 0;
 
@@ -3174,6 +3177,7 @@ void wxPropertyGrid::DoShowPropertyError( wxPGProperty* WXUNUSED(property), cons
     }
 #endif
 
+    /* TRANSLATORS: Caption of message box displaying any property error */
     ::wxMessageBox(msg, _("Property Error"));
 }
 
@@ -3306,6 +3310,7 @@ bool wxPropertyGrid::DoOnValidationFailure( wxPGProperty* property, wxVariant& W
             DoShowPropertyError(property, msg);
 
         if ( vfb & wxPG_VFB_SHOW_MESSAGEBOX )
+            /* TRANSLATORS: Caption of message box displaying any property error */
             ::wxMessageBox(msg, _("Property Error"));
     }