Use shrink_to_fit() to save memory space

ChangeLog

@@ -1,5 +1,6 @@
 2019-04-27  Markus Gans  <guru.mail@muenster.de>
 	* Add the reserve() method to FListBox to increase the capacity of the list
+	* Use shrink_to_fit() to save memory space
 
 2019-03-24  Markus Gans  <guru.mail@muenster.de>
 	* Add a "scroll view" chapter to the first steps document

src/ffiledialog.cpp

@@ -444,6 +444,7 @@ void FFileDialog::clear()
     std::free (entry.name);
 
   dir_entries.clear();
+  dir_entries.shrink_to_fit();
 }
 
 //----------------------------------------------------------------------

src/flistbox.cpp

@@ -286,6 +286,7 @@ void FListBox::clear()
 {
   std::size_t size;
   itemlist.clear();
+  itemlist.shrink_to_fit();
   current = 0;
   xoffset = 0;
   yoffset = 0;

src/fmenulist.cpp

@@ -93,6 +93,7 @@ void FMenuList::remove (int pos)
 void FMenuList::clear()
 {
   item_list.clear();
+  item_list.shrink_to_fit();
 }
 
 //----------------------------------------------------------------------

src/fobject.cpp

@@ -359,6 +359,7 @@ bool FObject::delAllTimer()
 
   timer_modify_lock = true;
   timer_list->clear();
+  timer_list->shrink_to_fit();
   timer_modify_lock = false;
   return true;
 }

src/fstatusbar.cpp

@@ -306,6 +306,7 @@ void FStatusBar::remove (int pos)
 void FStatusBar::clear()
 {
   key_list.clear();
+  key_list.shrink_to_fit();
 }
 
 //----------------------------------------------------------------------

src/ftextview.cpp

@@ -274,6 +274,7 @@ void FTextView::clear()
 {
   std::size_t size;
   data.clear();
+  data.shrink_to_fit();
   xoffset = 0;
   yoffset = 0;
   maxLineWidth = 0;

src/include/final/ftermbuffer.h

@@ -151,7 +151,10 @@ inline bool FTermBuffer::isEmpty() const
 
 //----------------------------------------------------------------------
 inline void FTermBuffer::clear()
-{ data.clear(); }
+{
+  data.clear();
+  data.shrink_to_fit();
+}
 
 //----------------------------------------------------------------------
 inline FTermBuffer& FTermBuffer::write()