Mark more characters shell-safe.

I still worry about just quoting things when passing it off to "ssh" or
"sh -c", so I'm being anal.  But _, ^ and , are certainly ok and while
both ~ and @ can have speacial meaning to shell/ssh they are benign.

connect.c

@@ -57,7 +57,9 @@ static char *shell_safe(char *url)
 		['A'...'Z'] = 1,
 		['.'] = 1, ['/'] = 1,
 		['-'] = 1, ['+'] = 1,
-		[':'] = 1
+		[':'] = 1, ['_'] = 1,
+		['@'] = 1, [','] = 1,
+		['~'] = 1, ['^'] = 1,
 	};
 
 	while ((c = *n++) != 0) {