Prefer compiler warnings to assertions for unhandled switch cases

Using 'default:' cases can hide logical errors which would lead to i3
crashes for users. With this change the compiler will print a warning
when a case is not handled. For example, if I add a new value in the
Font.type enum:
../../i3/libi3/font.c: In function ‘draw_text’:
../../i3/libi3/font.c:378:5: warning: enumeration value ‘NEWFONT’ not handled in switch [-Wswitch]
     switch (savedFont->type) {
     ^~~~~~

libi3/font.c

@@ -283,9 +283,6 @@ void free_font(void) {
             /* Free the font description */
             pango_font_description_free(savedFont->specific.pango_desc);
             break;
-        default:
-            assert(false);
-            break;
     }
 
     savedFont = NULL;
@@ -315,9 +312,6 @@ void set_font_colors(xcb_gcontext_t gc, color_t foreground, color_t background)
             pango_font_green = foreground.green;
             pango_font_blue = foreground.blue;
             break;
-        default:
-            assert(false);
-            break;
     }
 }
 
@@ -388,8 +382,6 @@ void draw_text(i3String *text, xcb_drawable_t drawable, xcb_gcontext_t gc,
             draw_text_pango(i3string_as_utf8(text), i3string_get_num_bytes(text),
                             drawable, visual, x, y, max_width, i3string_is_markup(text));
             return;
-        default:
-            assert(false);
     }
 }
 
@@ -425,8 +417,6 @@ void draw_text_ascii(const char *text, xcb_drawable_t drawable,
             draw_text_pango(text, strlen(text),
                             drawable, root_visual_type, x, y, max_width, false);
             return;
-        default:
-            assert(false);
     }
 }
 
@@ -519,8 +509,6 @@ int predict_text_width(i3String *text) {
             /* Calculate extents using Pango */
             return predict_text_width_pango(i3string_as_utf8(text), i3string_get_num_bytes(text),
                                             i3string_is_markup(text));
-        default:
+    }
     assert(false);
-            return 0;
-    }
 }

src/click.c

@@ -44,9 +44,6 @@ static bool tiling_resize_for_border(Con *con, border_t border, xcb_button_press
         case BORDER_BOTTOM:
             search_direction = D_DOWN;
             break;
-        default:
-            assert(false);
-            break;
     }
 
     bool res = resize_find_tiling_participants(&first, &second, search_direction, false);

src/con.c

@@ -1413,20 +1413,16 @@ orientation_t con_orientation(Con *con) {
             return HORIZ;
 
         case L_DEFAULT:
-            DLOG("Someone called con_orientation() on a con with L_DEFAULT, this is a bug in the code.\n");
+            ELOG("Someone called con_orientation() on a con with L_DEFAULT, this is a bug in the code.\n");
             assert(false);
-            return HORIZ;
 
         case L_DOCKAREA:
         case L_OUTPUT:
-            DLOG("con_orientation() called on dockarea/output (%d) container %p\n", con->layout, con);
+            ELOG("con_orientation() called on dockarea/output (%d) container %p\n", con->layout, con);
-            assert(false);
-            return HORIZ;
-
-        default:
-            DLOG("con_orientation() ran into default\n");
             assert(false);
     }
+    /* should not be reached */
+    assert(false);
 }
 
 /*

src/ipc.c

@@ -268,10 +268,6 @@ void dump_node(yajl_gen gen, struct Con *con, bool inplace_restart) {
         case CT_DOCKAREA:
             ystr("dockarea");
             break;
-        default:
-            DLOG("About to dump unknown container type=%d. This is a bug.\n", con->type);
-            assert(false);
-            break;
     }
 
     /* provided for backwards compatibility only. */