vac: add -a and -x flags

Thanks to Michael Kaminsky for the suggestion.

src/cmd/vac/testinc.c

@@ -0,0 +1,31 @@
+#include "stdinc.h"
+#include "vac.h"
+#include "dat.h"
+#include "fns.h"
+#include "error.h"
+
+void
+threadmain(int argc, char **argv)
+{
+	Biobuf b;
+	char *p;
+
+	ARGBEGIN{
+	default:
+		goto usage;
+	}ARGEND
+	
+	if(argc != 1){
+	usage:
+		fprint(2, "usage: testinc includefile\n");
+		threadexitsall("usage");
+	}
+	
+	loadexcludefile(argv[0]);
+	Binit(&b, 0, OREAD);
+	while((p = Brdline(&b, '\n')) != nil){
+		p[Blinelen(&b)-1] = 0;
+		print("%d %s\n", includefile(p), p);
+	}
+	threadexitsall(0);
+}