Fix compilation errors detected with gcc

src/app/color_swatches.cpp

@@ -29,12 +29,12 @@ ColorSwatches::ColorSwatches(const std::string& name)
 {
 }
 
-void ColorSwatches::addColor(Color& color)
+void ColorSwatches::addColor(const Color& color)
 {
   m_colors.push_back(color);
 }
 
-void ColorSwatches::insertColor(size_t index, Color& color)
+void ColorSwatches::insertColor(size_t index, const Color& color)
 {
   m_colors.insert(m_colors.begin() + index, color);
 }

src/app/color_swatches.h

@@ -35,8 +35,8 @@ public:
   const std::string& getName() const { return m_name; }
   void setName(std::string& name) { m_name = name; }
 
-  void addColor(Color& color);
+  void addColor(const Color& color);
-  void insertColor(size_t index, Color& color);
+  void insertColor(size_t index, const Color& color);
   void removeColor(size_t index);
 
   const Color& operator[](size_t index) const {

src/app/drop_files.cpp

@@ -37,6 +37,8 @@
   #include <winalleg.h>
 #endif
 
+namespace app {
+
 #ifdef ALLEGRO_WINDOWS
 
 #ifdef STRICT
@@ -45,8 +47,6 @@
   typedef FARPROC wndproc_t;
 #endif
 
-namespace app {
-
 static wndproc_t base_wnd_proc = NULL;
 static std::vector<base::string>* dropped_files;
 static base::mutex* dropped_files_mutex = NULL;

src/app/undoers/object_io.h

@@ -21,10 +21,7 @@
 
 #include "base/serialization.h"
 #include "base/unique_ptr.h"
-
+#include "undo/objects_container.h"
-namespace undo {
-  class ObjectsContainer;
-}
 
 namespace app {
   namespace undoers {

src/ui/manager.cpp

@@ -1009,7 +1009,7 @@ void Manager::pumpQueue()
 
     // Call Timer::tick() if this is a tick message.
     if (msg->type() == kTimerMessage) {
-      ASSERT(msg->timer.timer != NULL);
+      ASSERT(static_cast<TimerMessage*>(msg)->timer() != NULL);
       static_cast<TimerMessage*>(msg)->timer()->tick();
     }