Major Update: (compiling but untested)

- Replace CBuffer with CRollingBuffer and CShiftBuffer
  ShiftBuffer is faster and simpler and always zero terminates
- Updated SelectableCore to use RollingBuffer
- Add Overwrite parameter to Push() and ReadFromFD() methods
- Add PeakDirect() method for fast direct access to buffer

SelectableCore.h

@@ -92,8 +92,8 @@ struct SHandle {
     bool        KeepAlive; // Socket keep alive
 
     // Buffers
-    CBuffer     * InBuffer;
-    CBuffer     * OutBuffer;
+    CRollingBuffer  * InBuffer;
+    CRollingBuffer  * OutBuffer;
 
     // Input Markers
     char        * InMarker;