-c sequences=N suboptimal at N expression cutoff

N = 2:
  a;
  b;
  c;
  d;
was:
  a, b;
  c;
  d;
now:
  a, b;
  c, d;

fixes #1455
closes #1457

lib/compress.js

@@ -749,7 +749,10 @@ merge(Compressor.prototype, {
                 seq = [];
             };
             statements.forEach(function(stat){
-                if (stat instanceof AST_SimpleStatement && seqLength(seq) < compressor.sequences_limit) {
+                if (stat instanceof AST_SimpleStatement) {
+                    if (seqLength(seq) >= compressor.sequences_limit) {
+                        push_seq();
+                    }
                     seq.push(stat.body);
                 } else {
                     push_seq();

test/compress/sequences.js

@@ -169,3 +169,47 @@ for_sequences: {
         for (y = 5; false;);
     }
 }
+
+limit_1: {
+    options = {
+        sequences: 3,
+    };
+    input: {
+        a;
+        b;
+        c;
+        d;
+        e;
+        f;
+        g;
+        h;
+        i;
+        j;
+        k;
+    }
+    expect: {
+        a, b, c;
+        d, e, f;
+        g, h, i;
+        j, k;
+    }
+}
+
+limit_2: {
+    options = {
+        sequences: 3,
+    };
+    input: {
+        a, b;
+        c, d;
+        e, f;
+        g, h;
+        i, j;
+        k;
+    }
+    expect: {
+        a, b, c, d;
+        e, f, g, h;
+        i, j, k;
+    }
+}