Fix some signed/unsigned int comparison warnings from MSVC

src/sbbs3/scfg/scfg.c

@@ -1223,7 +1223,7 @@ void shell_cfg()
 	char str[128],code[128],done=0;
 	int j,k;
 	int i;
-	uint u;
+	int u;
 	static shell_t savshell;
 
 	while(1) {

src/sbbs3/scfg/scfgchat.c

@@ -207,7 +207,7 @@ void chan_cfg()
 	char str[128],code[128],done=0;
 	int j,k;
 	int i;
-	uint u;
+	int u;
 	static chan_t savchan;
 
 	while(1) {