Change cursor API to use RGBA data

This will allow us to use better formats that preserve the entire
alpha channel.
diff --git a/common/rfb/ConnParams.h b/common/rfb/ConnParams.h
index 9e647ba..517e649 100644
--- a/common/rfb/ConnParams.h
+++ b/common/rfb/ConnParams.h
@@ -77,7 +77,7 @@
     const char* name() const { return name_; }
     void setName(const char* name);
 
-    const Cursor& cursor() const { return cursor_; }
+    const Cursor& cursor() const { return *cursor_; }
     void setCursor(const Cursor& cursor);
 
     bool supportsEncoding(rdr::S32 encoding) const;
@@ -106,7 +106,7 @@
 
     PixelFormat pf_;
     char* name_;
-    Cursor cursor_;
+    Cursor* cursor_;
     std::set<rdr::S32> encodings_;
     char verStr[13];
     int verStrPos;