cameo: new command "reverse" to reverse all paths

Experimentally used to reverse tool direction in the smoothing pass.

cameo/lang.l

@@ -50,6 +50,7 @@ NUM	-?[0-9]+\.?[0-9]*
 <INITIAL>optimize		return TOK_OPTIMIZE;
 <INITIAL>remainder		return TOK_REMAINDER;
 <INITIAL>reset			return TOK_RESET;
+<INITIAL>reverse		return TOK_REVERSE;
 <INITIAL>rotate			return TOK_ROTATE;
 <INITIAL>stats			return TOK_STATS;
 <INITIAL>translate		return TOK_TRANSLATE;