Remove the `auto` specifier from `i` variable in `for` loops

`auto` is available in C++11+ compilers and this is not the case of a basic RPi setup.

src/Surfaces/SurfaceManager.cpp

@@ -382,7 +382,7 @@ void SurfaceManager::loadXmlSettings(string fileName) {
         }
 
         BaseSurface * SurfaceManager::selectSurface(BaseSurface * surface){
-            for (auto i = 0; i < surfaces.size(); i++) {
+            for (int i = 0; i < surfaces.size(); i++) {
                 if (surfaces[i] == surface){
                     selectedSurface = surface;
                     ofSendMessage("surfaceSelected");

src/Surfaces/SurfaceManagerGui.cpp

@@ -97,7 +97,7 @@ namespace ofx {
                     bSurfaceSelected = true;
                     
                     int jointIndex = -1;
-                    for (auto i = 0; i < textureEditor.getJoints().size(); i++) {
+                    for (int i = 0; i < textureEditor.getJoints().size(); i++) {
                         if (textureEditor.getJoints()[i] == hitJoint) {
                             jointIndex = i;
                             break;
@@ -138,7 +138,7 @@ namespace ofx {
                     hitJoint->select();
                     hitJoint->startDrag();
                     int jointVertIndex = 0;
-                    for (auto i = 0; i < projectionEditor.getJoints()->size(); i++) {
+                    for (int i = 0; i < projectionEditor.getJoints()->size(); i++) {
                         if ((*projectionEditor.getJoints())[i] == hitJoint) {
                             jointVertIndex = i;
                             break;