fix for order of evaluation breaks gs build.  this is likely a BUG, but i don't see it
just yet, and need to be doing other things.

Reference: /n/atom/patch/applied/cppreverteval
Date: Mon Mar 17 17:16:00 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/cpp/eval.c	Mon Mar 17 17:15:37 2014
+++ /sys/src/cmd/cpp/eval.c	Mon Mar 17 17:15:37 2014
@@ -122,7 +122,6 @@
 	op = ops;
 	*op++ = END;
 	for (rand=0, tp = trp->bp+ntok; tp < trp->lp; tp++) {
-	retry:
 		if(op >= ops + NSTAK)
 			sysfatal("cpp: can't evaluate #if: increase NSTAK");
 		switch(tp->type) {
@@ -162,12 +161,6 @@
 				}
 				continue;
 			}
-			if(tp->type==MINUS){
-				*op++ = UMINUS;
-				tp->type = PLUS;
-				goto retry;
-			}
-				
 			/* flow through */
 
 		/* plain binary */