Revised stack specific configurations

Adds the following functions for direct configuration of interface
- (set|get)stackopt
- (set|get)sockopt

LWIPInterface.cpp

@@ -213,16 +213,6 @@ int LWIPInterface::socket_close(void *handle)
 }
 
 
-int LWIPInterface::socket_set_option(void *handle, int optname, const void *optval, unsigned optlen)
-{
-    return NSAPI_ERROR_UNSUPPORTED;
-}
-
-int LWIPInterface::socket_get_option(void *handle, int optname, void *optval, unsigned *optlen)
-{
-    return NSAPI_ERROR_UNSUPPORTED;
-}
-
 int LWIPInterface::socket_bind(void *handle, const SocketAddress &address)
 {
     struct lwip_socket *s = (struct lwip_socket *)handle;

LWIPInterface.h

@@ -64,24 +64,6 @@ protected:
      */
     virtual int socket_close(void *handle);
 
-    /** Set socket options
-    \param handle   Socket handle
-    \param optname  Option ID
-    \param optval   Option value
-    \param optlen   Length of the option value
-    \return         0 on success, negative on failure
-    */    
-    virtual int socket_set_option(void *handle, int optname, const void *optval, unsigned int optlen);
-
-    /** Get socket options
-    \param handle   Socket handle
-    \param optname  Option ID
-    \param optval   Buffer pointer where to write the option value
-    \param optlen   Length of the option value
-    \return         0 on success, negative on failure
-    */
-    virtual int socket_get_option(void *handle, int optname, void *optval, unsigned int *optlen);
-
     /** Bind a server socket to a specific port
      *  @param handle   Socket handle
      *  @param address  Local address to listen for incoming connections on