'can not' -> 'cannot' in the source code.

src/config.cpp

@@ -444,7 +444,7 @@ config &config::child(const std::string& key, int n)
 	} else {
 		DBG_CF << "The config object has only »" << i->second.size()
 			<< "« children named »" << key
-			<< "«; request for the index »" << n << "« can not be honoured.\n";
+			<< "«; request for the index »" << n << "« cannot be honoured.\n";
 
 		return invalid;
 	}

src/display.cpp

@@ -2240,7 +2240,7 @@ void display::draw(bool update,bool force) {
 	// not this one, nobody will tell us to redraw (cleanup)
 	previous_invalidated_.swap(invalidated_);
 	invalidated_.insert(previous_invalidated_.begin(),previous_invalidated_.end());
-	// these new invalidations can not cause any propagation because
+	// these new invalidations cannot cause any propagation because
 	// if a hex was invalidated last turn but not this turn, then
 	// * case of no unit in neighbor hex=> no propagation
 	// * case of unit in hex but was there last turn=>its hexes are invalidated too

src/gui/widgets/window.cpp

@@ -1424,7 +1424,7 @@ void twindow::signal_handler_request_placement(
  * a global overview of some terms used in this document.
  *
  * - @ref gui2::twidget "Widget"; Any item which can be used in the widget
- *   toolkit. Not all widgets are visible. In general widgets can not be
+ *   toolkit. Not all widgets are visible. In general widgets cannot be
  *   sized directly, but this is controlled by a window. A widget has an
  *   internal size cache and if the value in the cache is not equal to 0,0
  *   that value is its best size. This value gets set when the widget can

src/tools/schema/sourceparser.cpp

@@ -319,7 +319,7 @@ bool class_source_parser::parse_source(){
 
 	f_.open(input_.c_str(),std::ios::in);
 	if (f_.fail()){
-		errors_.add_simple_error("File "+input_ + " can not be opened\n");
+		errors_.add_simple_error("File "+input_ + " cannot be opened\n");
 		return false;
 	}
 	line_ = 0;