Fix Debian GCC7 FTBFS: remove default constructors

src/terminal/terminalframebuffer.cc

@@ -45,15 +45,6 @@ Cell::Cell( color_type background_color )
     fallback( false ),
     wrap( false )
 {}
-Cell::Cell() /* default constructor required by C++11 STL */
-  : contents(),
-    renditions( 0 ),
-    wide( false ),
-    fallback( false ),
-    wrap( false )
-{
-  assert( false );
-}
 
 void Cell::reset( color_type background_color )
 {
@@ -358,12 +349,6 @@ Row::Row( const size_t s_width, const color_type background_color )
   : cells( s_width, Cell( background_color ) ), gen( get_gen() )
 {}
 
-Row::Row() /* default constructor required by C++11 STL */
-  : cells( 1, Cell() ), gen( get_gen() )
-{
-  assert( false );
-}
-
 uint64_t Row::get_gen() const
 {
   static uint64_t gen_counter = 0;

src/terminal/terminalframebuffer.h

@@ -93,9 +93,10 @@ namespace Terminal {
     unsigned int fallback : 1; /* first character is combining character */
     unsigned int wrap : 1;
 
+  private:
+    Cell();
   public:
     Cell( color_type background_color );
-    Cell(); /* default constructor required by C++11 STL */
 
     void reset( color_type background_color );
 
@@ -208,8 +209,10 @@ namespace Terminal {
     // in scrolling.
     uint64_t gen;
 
+  private:
+    Row();
+  public:
     Row( const size_t s_width, const color_type background_color );
-    Row(); /* default constructor required by C++11 STL */
 
     void insert_cell( int col, color_type background_color );
     void delete_cell( int col, color_type background_color );