Make lex safer for 8-bit data.
 [rsc] --rw-rw-r-- M 1487869 glenda sys 4074 Jan 29 11:18 sys/src/cmd/lex/ncform
	/n/sourcesdump/2006/0129/plan9/sys/src/cmd/lex/ncform:9,15 - 
	/n/sourcesdump/2006/0130/plan9/sys/src/cmd/lex/ncform:9,15
	  extern struct yysvf *yyestate;
	  int yyprevious = YYNEWLINE;
	  # ifdef LEXDEBUG
	- extern void allprint(char);
	+ extern void allprint(int);
	  # endif
	  yylook(void){
	  	struct yysvf *yystate, **lsp;
	/n/sourcesdump/2006/0129/plan9/sys/src/cmd/lex/ncform:113,119 - 
	/n/sourcesdump/2006/0130/plan9/sys/src/cmd/lex/ncform:113,119
	  			}
	  # ifdef LEXDEBUG
	  		if(debug){
	- 			fprintf(yyout,"stopped at %d with ",*(lsp-1)-yysvec-1);
	+ 			fprintf(yyout,"stopped at %d with ",lsp>yylstate?*(lsp-1)-yysvec-1:0);
	  			allprint(yych);
	  			putchar('\n');
	  			}
 [rsc] --rw-rw-r-- M 1487869 glenda sys 10162 Jan 29 11:18 sys/src/cmd/lex/sub1.c
	/n/sourcesdump/2006/0129/plan9/sys/src/cmd/lex/sub1.c:462,467 - 
	/n/sourcesdump/2006/0130/plan9/sys/src/cmd/lex/sub1.c:462,469
	  void
	  allprint(int c)
	  {
	+ 	if(c < 0)
	+ 		c += 256;	/* signed char */
	  	switch(c){
	  		case 014:
	  			print("\\f");