[ns] Compile NS-2 on Redhat 8.0

[HE Jun]

Hi, I just compiled ns-2 (ns-2 July 27, 2002 snapshot version)
successfully. The following are the changes I made. 

1. nix/nixnode.cc
	line 130: 
	     	if (prev == NULL) // ! How can this happen?
	===>    if (prev == m_Adj.end() ) // ! How can this happen?

2. linkstate/ls.cc
	line 647:
		bool LsRouting::sendLinkStates(bool buffer = false ) 
	===> 	bool LsRouting::sendLinkStates(bool buffer )

3. pgm/pgm-sender.cc
	line 293:
		void PgmSender::sendmsg(int nbytes, const char *flags = 0)
	===>    void PgmSender::sendmsg(int nbytes, const char *flags)

4. diffusion3/lib/nr/nr.cc
	line 68:
		 NRAttrVec::iterator *place = NULL) {
	===>	 NRAttrVec::iterator *place ) {

5. diffusion3/lib/dr.cc
	line 73:
		int DiffusionRouting::getAgentId(int id = -1) {
	===>	int DiffusionRouting::getAgentId(int id ) {
	line 710:
		u_int16_t priority = FILTER_KEEP_PRIORITY)
	===>	u_int16_t priority )

5. routing/route.h 
	line 81	
		inline int elements_in_level (int *addr, int level);
	===>   	int elements_in_level (int *addr, int level);

6. emulate/inet.c 
	
	change filename to inet.cc 
	
	line 130: change c-style function definition of in_cksum to 
		u_short in_cksum(u_short *addr,int len)

7. Makefile
	line 303:
		move emulate/inet.o from OBJ_EMULATE_C section to OBJ_EMULATE_CC
section