Patch from issue 1012: Proposal of an icon theme for RT

This patch add multiple iconset capabilities, on a per theme basis. See comment #61 and #68 from issue 1012 to see how it works.

rtgui/main.cc

@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <options.h>
 #include <soundman.h>
+#include <rtimage.h>
 #include "version.h"
 
 #ifndef WIN32
@@ -137,6 +138,8 @@ int main(int argc, char **argv)
    }
    Gtk::Main m(&argc, &argv);
 
+   RTImage::setPaths(options);
+
 #ifndef WIN32
    // For an unknown reason, gtkmm 2.22 don't know the gtk-button-images property, while it exists in the documentation...
    // Anyway, the problem was Linux only